Hi Yogesh,

Use the below code for show list of SObject and related field API & data type. 

Component===>

<aura:component controller="PickListOfobject">
    <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
    <aura:attribute name="objInfo" type="List"/>
    <aura:attribute name="selectObjRelatedField" type="List"/>
    <aura:attribute name="apiName" type="String[]"/>
    <div class="slds-grid slds-wrap">
        <div class="slds-col slds-size_6-of-12">
            <span>
                <lightning:select aura:id = "selectObj" onchange="{!c.doSomething}"  label="Choose SObject:">
                    <aura:iteration items="{!v.objInfo}" var="vr">
                        <option value="{!vr}">{!vr}</option>
                    </aura:iteration>
                </lightning:select>
            </span>
        </div>
        <div class="slds-col slds-size_6-of-12">
            <span>
                <lightning:select aura:id = "selectField" onchange="{!c.ShowApi}"  label="Choose Field:">
                    <aura:iteration items="{!v.selectObjRelatedField}" var="vrr">
                        <option value="{!vrr}">{!vrr}</option>
                    </aura:iteration>
                </lightning:select>
            </span>
        </div>
    </div> 
    <div class="slds-grid slds-grid_pull-padded-medium">
        <div class="slds-col slds-p-horizontal_medium">
            <span Style="margin-left:50px; margin-top:45px;">
                <aura:iteration items="{!v.apiName}" var="vrR" indexVar="key">
                    {!vrR}
                </aura:iteration>
            </span>
        </div>
    </div>
</aura:component>

JS controller===>

({
    doInit : function(component, event, helper)
    {
        console.log('doInit   called::');
       helper.fetchPickListVal(component, event, helper); 
    },
    doSomething : function(component, event, helper)
    {
        console.log('doSomething   called::');
        helper.doSomethinghelper(component, event, helper);
    },
    ShowApi : function(component, event, helper)
    {
        console.log('ShowApi   called::');
        helper.ShowApihelper(component, event, helper);
    }
})

Helper controller===>

({
    fetchPickListVal: function(component, event, helper) {
        console.log('fetchPickListVal   called::');
        var pickVal = component.get("c.getAllObjects");
        pickVal.setCallback(this, function(response) {
            var state = response.getState();
            console.log('selectedValue   :::'+state);
            if (component.isValid() && state === "SUCCESS") {
                component.set("v.objInfo", response.getReturnValue());
                
            }
            else {
                console.log("Failed with state: " + state);
            }
        });
        $A.enqueueAction(pickVal);
    },
    doSomethinghelper : function(component, event, helper){
        console.log('doSomethinghelper   called::');
        var pickVal = component.get("c.getTestOptions");
        var selectValue123 = component.find("selectObj").get("v.value");
        console.log('selectedValue   :::'+selectValue123);
        pickVal.setParams({
            "selectValue" : selectValue123
        });
        pickVal.setCallback(this, function(response) {
            var state = response.getState();
            if (component.isValid() && state === "SUCCESS") {
                component.set("v.selectObjRelatedField", response.getReturnValue());
            }
            else {
                console.log("Failed with state: " + state);
            }
        });
        $A.enqueueAction(pickVal);
    },
    ShowApihelper : function(component, event, helper){
        console.log('ShowApihelper   called::');
        var pickVal = component.get("c.getApiName");
        var selectValue = component.find("selectObj").get("v.value");
        var selectFieldObj = component.find("selectField").get("v.value");
        
        
        console.log('selectedValuesss   :::'+selectFieldObj);
        pickVal.setParams({
            "selectObj" : selectValue,
            "selectField" : selectFieldObj
        });
        pickVal.setCallback(this, function(response) {
            var state = response.getState();
            var array = [];
            array = response.getReturnValue().split(',');
            console.log("Failed Todayt: " + state);
            if (component.isValid() && state === "SUCCESS") {
                component.set("v.apiName", array);
            }
            else {
                console.log("Failed with state: " + state);
            }
        });
        $A.enqueueAction(pickVal);
    }
})

 Apex Controller===>>


public class PickListOfobject {
    @AuraEnabled
    public static List<String> getAllObjects(){
        List<string> SObjectList = new List<string>();
        for(Schema.SObjectType objTyp : Schema.getGlobalDescribe().Values()){
            String name = objTyp.getDescribe().getName();
            String Label = objTyp.getDescribe().getLabel();
            SObjectList.add(name);
            SObjectList.add(Label);
            System.debug( 'Name : ' + name);
        }
        return SobjectList; 
    }
    @AuraEnabled
    public static List<String> getTestOptions(String selectValue){
        String ObjectName = selectValue;
        List<String> FieldList = new List<String>();
        Map<String , Schema.SObjectType> schemaGlobalDescription = Schema.getGlobalDescribe();
        Schema.sObjectType objType = schemaGlobalDescription.get(ObjectName); 
        Schema.DescribeSObjectResult objDescribeSObjectResult = objType.getDescribe(); 
        Map<String , Schema.SObjectField> mapFieldList = objDescribeSObjectResult.fields.getMap(); 
        for(Schema.SObjectField field : mapFieldList.values()) 
        { 
            Schema.DescribeFieldResult fieldResult = field.getDescribe(); 
            if(fieldResult.isAccessible())
            {
                System.debug(fieldResult.getName());
                FieldList.add(fieldResult.getLabel());
            }
        }
        return FieldList;
    }
    @AuraEnabled
    public static String getApiName(String selectObj , String selectField){
        system.debug('fieldss::'+selectField);
        system.debug('object::'+selectObj);
        List<String> FieldDetail = New List<String>();
        SObjectType type = Schema.getGlobalDescribe().get(selectObj);
        Map<String,Schema.SObjectField> mfields = type.getDescribe().fields.getMap();
        for(String strField:mfields.keySet())
        {
            Schema.DisplayType fielddataType = mfields.get(strField).getDescribe().getType();
            SObjectField fl = mfields.get(strField);
            if(selectField == fl.getDescribe().getlabel())
            {
                system.debug('datatype::'+fielddataType);
                return +'API Name : '+strField +' DataType : '+fielddataType;
               
            }
        }
        return null;
    }
}

I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too.

Thanks and Regards,
Ajay Dubedi
www.ajaydubedi.com