I need to migrate a single updated Apex Class (currently in our Sandbox) into our Production org.  Not being a developer, I am trying to understand what the Test options, that appear as part of the Inbound Change Set process, actually mean - "Default, Run Local Tests, Run All Tests, Run Specific Tests"?  
I'm trying to understand what I need to do to ensure that my Inbound Change Set (containing the one updated Apex Class) is migrated to our Production org successfully.
Any help or guidance on this would be appreciated.  Thank you

I would like to view a Change Set (containing an Apex Class) that was created and deployed last year 2019.  Is there any place in Salesforce where I can find a history of either Outbound or Inbound change sets for this time period or for any previous time period?  Thank you.  

I need to replace a Formula (type=Number) field with a straight NUMBER field.  The Formula field is referenced in a handful of reports and in one Apex class. Trying to understand the best way (steps) to accomplish this considering the restrictions associated with changing field types.
Do I attempt to change the field type or create a new field?  Any suggestions?  Thank you.    

Hi All.
We received the following (see below) certificate expiration notice but when I look for this in our Certificate and Key Management section, within Setup, I am NOT able to find any such certificate with this Expiration Date.  Should I be looking elsewhere?  
Thank you for your time and advice.

"You have one or more certificates in your Salesforce org Navin, Haffty & Associates 00D2E000000no3I that will expire soon. Review the list below and visit Certificate and Key Management from Setup to make an update.

- SelfSignedCert_15Apr2019_184313, Self-Signed, expires on 4/15/2020. Warning: This certificate will expire in 30 day(s)."

I would like to view a Change Set (containing an Apex Class) that was created and deployed last year 2019.  Is there any place in Salesforce where I can find a history of either Outbound or Inbound change sets for this time period or for any previous time period?  Thank you.  

I need to replace a Formula (type=Number) field with a straight NUMBER field.  The Formula field is referenced in a handful of reports and in one Apex class. Trying to understand the best way (steps) to accomplish this considering the restrictions associated with changing field types.
Do I attempt to change the field type or create a new field?  Any suggestions?  Thank you.    

Hi All.
We received the following (see below) certificate expiration notice but when I look for this in our Certificate and Key Management section, within Setup, I am NOT able to find any such certificate with this Expiration Date.  Should I be looking elsewhere?  
Thank you for your time and advice.

"You have one or more certificates in your Salesforce org Navin, Haffty & Associates 00D2E000000no3I that will expire soon. Review the list below and visit Certificate and Key Management from Setup to make an update.

- SelfSignedCert_15Apr2019_184313, Self-Signed, expires on 4/15/2020. Warning: This certificate will expire in 30 day(s)."