Travel ban restrictions?

There is no indication that relative petitions will be affected. We will need to wait and see.

Volunteering is not permitted when the volunteering could have been a paid position. That is the United States citizen worker or lawful permanent...

The petition will be sent to the NVC. The NVC will notify you with requests for payment and information and evidence.

3 months in the state or USCIS district where you claim residence requirement - N400 USCIS

Inform them immediately at the interview of the error and provide evidence.

Name Change on a Green Card?

Generally 3-6 months, however, recently cases are taking longer for most filings.

Should i call to correct a mistake of question question 7 part 12, N400 form?

Calling will not accomplish what needs to be done. When interviewed let the examiner know right away and provide evidence.

Have an immigration attorney review the reason for the refusal and asses what transpired and go from there.

This is not an immigration question. The question should be directed to a tax attorney or accountant. The instructions for applying are available...

If there is an error in the notarized copy of a marriage certificate, can I still use it for GC application?

Have a proper copy made and notarized. Small errors often result in big issues.

Am I able to travel outside of the country and return while my H1 Amendment RFE is still pending?

The person in the best position to advise you is the immigration attorney that prepared the response to the RFE for your employer.