Getting too many send email invocation error even though i am sending email to one email address. Objective of the below code is to show a list in form of table and send email of that list in form of excel to the email address entered. The below code worked fine till i used pagination after which "Too many email invocation" error occured.
Below are my codes.
Apex class:
//will show 1000 eror
public class PieController {
    
    public String result{get;set;}
    public String qString{get;set;}
    public list<TerritoryBkp__c> result1{get;set;}
    public list<TerritoryBkp__c> result2{get;set;}
   // public List<List<TerritoryBkp__c>> result3{get;set;}
   public Set<String> terrSet =new Set<String>();
   public Set<String> terrBkpSet = new Set<String>();
   public Set<String> missingSetData = new Set<String>();
   public Set<String> nameSet = new Set<String>();
   public String terr =null;
   public String terr_bkp=null;
   public String subString=null;
   public String s1=null;
public List<wrapper> lstwrapper {get; set;}
    public string Filetype{get;set;}
    public string header{get;set;}
   public boolean res{get;set;}
    public String finalstr{get;set;}
    public String message{get;set;}
    public integer i{get;set;}
    public integer countTerr{get;set;}
    public integer countMismatch{get;set;}
   public integer counter=0;
    public integer list_size=30;
    
    
public void PieController() //replace with T2
    {
     countTerr=0;   
     i=0;
    List<Territory2> terrList = [SELECT Id,MSD_CORE_Country_Code__c,MSD_CORE_ParentTerritory1Id__c,Name from Territory2];
    List<TerritoryBkp__c> terrBkpList = [SELECT Id,MSD_CORE_Country_Code__c,MSD_CORE_Parent_Territory__c,Name from TerritoryBkp__c];
    res=false;
    
  
    for( Territory2 t: terrList) //replace with T2
    {
    terr=t.Name+'@'+t.MSD_CORE_Country_Code__c+'@'+t.MSD_CORE_ParentTerritory1Id__c; 
    terrSet.add(terr);
    }
    system.debug('Territory1 set----'+terrSet);
    system.debug('Territory1 SIZEEE----'+terrSet.size());
    for( TerritoryBkp__c t1: terrBkpList)
    {
    terr_bkp=t1.Name+'@'+t1.MSD_CORE_Country_Code__c+'@'+t1.MSD_CORE_Parent_Territory__c;
    terrBkpSet.add(terr_bkp);
    }
    system.debug('TerritoryBkp set----'+terrBkpSet);
    system.debug('TerritoryBkp SIZEEE----'+terrBkpSet.size());
    If(terrSet.size()==terrBkpSet.size())
    {
    If(terrSet.equals(terrBkpSet))
    {
    result='Verified! Territory table contains all data.';
  system.debug('Result-->'+result);
    }
    else{
        excecute(); 
    }
    }
    
    else
    {
    excecute();
        system.debug('Res in line 60-->'+res);
    }
    
    }
    public void excecute()
    {    res=true;
     i=1;
     countTerr=[select count() from TerritoryBkp__c];
     system.debug('Res in line 66_executemethod-->'+res);
       Filetype = '';
    lstwrapper = new List<wrapper>();
    header = 'Id,Territory Name,ParentTerritory Id,Country Code';
    finalstr = header ;
      
    result='Oops!Few data missing from Territory2 table. Please find the list of missing rows.';
    for(String s:terrBkpSet)
    {  
               if(!terrSet.contains(s)) 
               {
                missingSetData.add(s);
            }
    
}
         Iterator<String> itr = missingSetData.iterator();
        while(itr.hasNext()){
            s1=itr.Next();
            integer iend = s1.indexOf('@');
            
            if (iend != -1) 
            {
                subString= s1.substring(0 , iend);
            
            }
            nameSet.add(subString);
        }  
        result1=[Select t.Id, t.Name, t.MSD_CORE_Parent_Territory__c,t.MSD_CORE_Country_Code__c from TerritoryBkp__c t where t.Name=:nameSet];
     countMismatch=result1.size();  
     result2=[Select t.Id, t.Name, t.MSD_CORE_Parent_Territory__c,t.MSD_CORE_Country_Code__c from TerritoryBkp__c t where t.Name=:nameSet limit :list_size offset:counter];
     for(TerritoryBkp__c lw:result1)    
    {
        wrapper w = new wrapper();
        w.TerrId= lw.Id;
        w.TerrName= lw.Name;
        w.TerrParentId=lw.MSD_CORE_Parent_Territory__c;
        w.TerrCountryCode=lw.MSD_CORE_Country_Code__c;
        lstwrapper.add(w);  
        string recordString = '"'+lw.id+'","'+lw.Name+'","'+lw.MSD_CORE_Parent_Territory__c+'","'+lw.MSD_CORE_Country_Code__c +'"\n';
        finalstr = finalstr +recordString;

    }
 // sendEmail();   
     
    }
    public List<PieWedgeData> getPieData() {
        List<PieWedgeData> data = new List<PieWedgeData>();
        data.add(new PieWedgeData('Before TM2.0', countTerr));
        data.add(new PieWedgeData('Mismatched after TM2.0', countMismatch));
       return data;
    }
    
 public void sendEmail()
 {
     try{
   Messaging.EmailFileAttachment csvAttc = new Messaging.EmailFileAttachment();
blob csvBlob = Blob.valueOf(finalstr);
string csvname= 'MissingTerrData.csv';
csvAttc.setFileName(csvname);
csvAttc.setBody(csvBlob);
Messaging.SingleEmailMessage email =new Messaging.SingleEmailMessage();
String[] toAddresses = new list<string> {qString};
//String toAddresses=qString;
String subject ='Territory Mismatch Data CSV';
String body='Hi,\n';
body+='Please find attached the list of mismatched or missing territories.\n';
body += '\n Thank You,' ;
email.setSubject(subject);
email.setToAddresses( toAddresses );
email.setPlainTextBody(body);
email.setFileAttachments(new Messaging.EmailFileAttachment[]{csvAttc});
if(!(String.isBlank(qString)))
{
Messaging.SendEmail(new Messaging.SingleEmailMessage[] {email});                    
Messaging.SendEmailResult [] r = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email}); 
if(r[0].IsSuccess() == true){
 message = 'Email Sent!'; 
}
}  
     } catch(Exception e){
        
         message = 'Please enter Email Address';
     }
 }
    public PageReference Beginning() { //user clicked beginning
      counter = 0;
        excecute();
      return null;
   }

   public PageReference Previous() { //user clicked previous button
      counter -= list_size;
       excecute();
      return null;
   }

   public PageReference Next() { //user clicked next button
      counter += list_size;
        excecute();
      return null;
   }

   public PageReference End() { //user clicked end
      counter = countMismatch - math.mod(countMismatch, list_size);
        excecute();
      return null;
   }

   public Boolean getDisablePrevious() { 
      //this will disable the previous and beginning buttons
      if (counter>0) return false; else return true;
   }

   public Boolean getDisableNext() { //this will disable the next and end buttons
      if (counter + list_size < countMismatch) return false; else return true;
   }

   public Integer getTotal_size() {
      return countMismatch;
   }

   public Integer getPageNumber() {
      return counter/list_size + 1;
   }

   public Integer getTotalPages() {
      if (math.mod(countMismatch, list_size) > 0) {
         return countMismatch/list_size + 1;
      } else {
         return (countMismatch/list_size);
      }
   }
     
    public class wrapper{
        public string TerrId {get; set;}
        public string TerrName{get; set;}
        public string TerrParentId{get; set;}
        public string TerrCountryCode{get; set;}
      //  public string dateval{get; set;}
      
    }
      
  
    public class PieWedgeData {

        public String Name { get; set; }
        public Integer Data { get; set; }

        public PieWedgeData(String Name, Integer Data) {
            this.Name = Name;
            this.Data = Data;
        }
    
}
    
}

Visualforce Page: 
<apex:page controller="PieController" title="Territory Verification" sidebar="false" showHeader="false" readOnly="true">
<style>

    .activeTab {background-color: #236FBD; color:white; background-image:none;font-size: 14px}
    .inactiveTab { background-color: lightgrey; color:black; background-image:none;font-size: 14px}
    .headerRow .TableTitle {
    background-color: #236FBD !important;
    background-image: none !important;
    color: #black !important; 
    font-size:100% !important; 
   }
.changecss
{
background-image: none !important;
background-color:lightblue !important;
    color:blue !important;

}
    .buttonclass
    {
    color:white !important;
background:#00CC00 !important;
border-left: 0px  !important;
border-top: 0px  !important;
border-bottom: 0px  !important;
border-right: 0px  !important;
    }
#ct{

        text-align:center;

        font-size: 25px;
    }

    </style>
<apex:form style="border-style:solid;border-width:2px;
                      border-color:black;background-color:lightgrey" id="form1">
    
<div style="background-color:LightBlue;">
<div id="ct" >
<h1>Territory Verification</h1>
</div>
    <apex:commandButton styleClass="buttonclass" value="Back" oncomplete="doRedirect();"/>
    <script type="text/javascript">
                function doRedirect(){
                    window.history.back();
                }

            </script>
    </div>

    <apex:pageBlock id="pg">
        
<apex:tabPanel switchType="client" selectedTab="name1" id="dataTabPanel" tabClass="activeTab" inactiveTabClass="inactiveTab">
    <b><apex:tab label="Territory Verification" name="name1" id="tabOne">
        <div style="text-align:center;font-size: 12px;color:green;">
        <b><apex:outputLabel value="{!message}" rendered="true"></apex:outputLabel></b> <br/>
        </div>
        <b> <apex:outputLabel value="Click here to verify data"></apex:outputLabel></b>
        <b> <apex:commandButton styleClass="buttonclass" value="Verify data" action="{!PieController}" rendered="true"/> </b><br/><br/>
        <b><apex:outputLabel value="Enter Email address to send data in your inbox!"/></b><br/><br/>
        <apex:inputTextarea style="width: 300px; height: 40px;" id="email" value="{!qString}"/>    
        <b> <apex:commandButton styleClass="buttonclass" value="Send Email" action="{!sendEmail}" rendered="true"/> </b><br/>
        <br/>
    </apex:tab>
    </b>
   
    <!--<apex:tab label="Export missing data list,if any" name="name2" id="tabTwo">
    <apex:commandButton value="Click here to Export" action="{!missingData}" rendered="true" rerender="true"/>
       </apex:tab>-->
       </apex:tabPanel>
   <apex:outputPanel id="thepanel">
           
            <b><apex:outputLabel value="{!result}" style="color:{!IF(AND(i!=NULL,i>0),'red','green')};"></apex:outputLabel></b> <br/><br/>
            <apex:pageBlockTable id="s1" rowClasses="changecss" value="{!result2}" var="t" rendered="{!res}">
            
                <apex:column headerClass="TableTitle" value="{!t.Id}" />
                <apex:column headerClass="TableTitle" value="{!t.Name}"/>
                <apex:column headerClass="TableTitle" value="{!t.MSD_CORE_Country_Code__c}"/>
                <apex:column headerClass="TableTitle" value="{!t.MSD_CORE_Parent_Territory__c}"/>
                
                <apex:facet name="footer">Showing Page # {!pageNumber} of {!totalPages}</apex:facet>
                
       </apex:pageBlockTable>
        
              </apex:outputPanel>
     <!--   <div align="right">
             
        <apex:commandButton action="{!Beginning}" title="Beginning" value="<<" disabled="{!disablePrevious}"/>
        <apex:commandButton action="{!Previous}" title="Previous" value="<" disabled="{!disablePrevious}" />        
        <apex:commandButton action="{!Next}" title="Next" value=">" disabled="{!disableNext}"/>
        <apex:commandButton action="{!End}" title="End" value=">>" disabled="{!disableNext}"/> 
        </div>-->
   <!--      <div align="right">
             
        <apex:commandButton action="{!Beginning}" title="Beginning" value="<<" disabled="{!disablePrevious}" reRender="s1"/>
        <apex:commandButton action="{!Previous}" title="Previous" value="<" disabled="{!disablePrevious}" reRender="s1"/>        
        <apex:commandButton action="{!Next}" title="Next" value=">" disabled="{!disableNext}" reRender="s1"/>
        <apex:commandButton action="{!End}" title="End" value=">>" disabled="{!disableNext}" reRender="s1"/> 
        </div>-->
        <apex:outputPanel rendered="{!If(res = true, true, false)}">
            <div align="right">
             
        <apex:commandButton action="{!Beginning}" title="Beginning" value="<<" disabled="{!disablePrevious}"/>
        <apex:commandButton action="{!Previous}" title="Previous" value="<" disabled="{!disablePrevious}" />        
        <apex:commandButton action="{!Next}" title="Next" value=">" disabled="{!disableNext}"/>
        <apex:commandButton action="{!End}" title="End" value=">>" disabled="{!disableNext}"/> 
        </div>
            <div>
              <b><h>Chart View:</h></b>  
            </div>
            <div style="text-align:center;font-size: 12px;color:green;">
             
            <apex:chart height="350" width="450" data="{!pieData}">
        <apex:pieSeries dataField="Data" labelField="Name"/>
        <apex:legend position="right"/>
    </apex:chart>
                   
            </div>
        </apex:outputPanel>
         
        <apex:image style="margin-top:50px;margin-left:1000px;" url="https://apmsd--apswatt1--c.visualforce.com/resource/1597122238000/ETM_Tool_Logo" width="15%" height="15%"/><br/>
    </apex:pageBlock>
</apex:form>
</apex:page>

In the object specific challenge, i wrote the below code:


And also checked the available for mobile app checkbox:


And yet, in contact, while creating a new action, i cannot see the showassistant info visualforce page in the list. Please suggest what am i missing.

In the object specific challenge, i wrote the below code:


And also checked the available for mobile app checkbox:


And yet, in contact, while creating a new action, i cannot see the showassistant info visualforce page in the list. Please suggest what am i missing.