All the answers for the questions that I asked is provided in the apple document in this pdf. For those who are too lazy to read the entire document to get the answer, below are the answers to my question from the document.
The document says
Distribution provisioning profiles expire 12 months after they’re issued. After the expiration date, the profile is removed and the app won’t launch. When your distribution certificate expires, the app won’t launch. Your distribution certificate is valid for three years from when it was issued, or until your Enterprise Developer Program membership expires, whichever comes first.
You can have two distribution certificates active at the same time; each is independent from the other. The second certificate is intended to provide an overlapping period during which you can update your apps before the first certificate expires. When requesting your second distribution certificate from the iOS Dev Center, be sure you don’t revoke your first certificate.
Revoking a distribution certificate invalidates all of the apps you’ve signed with it. You should revoke a certificate only as a last resort—if you’re sure the private key is lost or the certificate is believed to be compromised.