File a FOIA request to obtain a copy of the immigration file.

No you should have a stamp before travel.

Marriage is not a requirement for the parents to be petitioned.

Yes you may do so and inquire about current status.

What is your question? Please rephrase for clarity.

The interview would likely be rescheduled if first time.

More information is needed about your status to make such determination. Consult with an attorney for guidance.

It will likely take 2 years given processing at all phases.

I agree with my colleagues re: limited options once documents have been submitted for 221g review.

Best to use the USCIS webpage for current processing times.