Does it matter when I do my medical exam after I submit my I-485 application for green card through marriage ?

You can obtain the Medical Exam result within just a few days, so probably better to get after you have received notice of the interview.

H1B counselar processing and i94

If you chose to join the new company for whom an extension of status was not approved (only a new H-1B Petition) you would have to depart the US...

What will happen if I travel while my H1B extension of status is pending with USCIS?

You will; need the original approval notice for the extension when seeking stamping in your passport.

Can I get an I-551 stamp if my green card was stolen?

You could file for naturalization with at least a copy of the your green card, but filing an I-90 would be recommended.

Discovered typo in DS 160 after visa stamping?

You will need to obtain a correction of the date on the visa, at least before the next return.

Yes, you must mention the marriage even though it was annulled.

How long does NVC take to schedule an interview after assigning consulate? Our consulate is nepal

It depends how quickly you provide all necessary documents and pay the associated fees. Usually, it takes 3-6 months to schedule interview once...

Form I-130 Part 5?

Insert the approval date. It should not make a difference.

Should I use H1B visa to enter U.S. after AOS interview finished but priority date not current due to retrogression?

If you would prefer to remain in H-1B status,. you should use the H-1B/H-4 visas. Consult with your immigration attorney for the pros and cons.

Changing employer in H1-B after my I-140 approved?

You may continue to extend your H-1B beyond the 6th year if the approved I-140 remains valid. A subsequent I-140 should also retain the priority...