1. Can i still work with my old employer ( Employer A) and decline new offer with Employer B. YES 2. My Current Employer files my I485 in Sep...

There's no such publicly-available statistics.

Yes you may resubmit a form AR-11, as needed.

If the program sponsor approves. It is also advisable that you privately consult with an experienced immigration attorney to discuss your options.

Submit paperwork explaining the discrepancy.

USCIS will likely consider volunteering unauthorized employment.

You can enter with a negative COVID test and/or quarantine.

Check processing times. Put in a service request, if over processing times.

I agree with the previous responses. It is also advisable that you privately consult with an experienced immigration attorney to discuss your options.

Your fiancé can quarantine in another country for 14 days, then enter the US, Also consider filing a fiancé visa.