In a complicated scenario like yourself with uncertainties, try to break into simpler things first.
AOS Pending Status: It is where you have an I-485 receipt number. By itself, a) it does not allow you to work and b) it does not allow you to reenter the country. There is no requirement of work.
AOS Pending + EAD: EAD allows you to work when you are in AOS pending status.
AOS Pending + AP: It allows you to travel out of the country without abandoning your I485. If you travel without AP, you are in serious jeopardy unless you have another status such as H1, L1, etc., See
AP Travel thread for more info.
AC21 or INA Section 204(j): It grants you ?job portability? after 180 days of pending I485 from ?Received Date? on I485 form I797 receipt notice.
I485 Supplement J: First understand that I485 / GC is for a future job that is stated on PERM. The first time you file I485, Supp J is for confirmation of Bona Fide Job Offer. After 180 days if you send Supp J it is a request for Job Portability Under INA Section 204(j) / AC21.
The moment you talk about AC21, the first rule is no matter what you have to meet the 180 day requirement. After 180 days, you are a "free agent" and you can go and work for any employer as long as the job is in ?same or similar? category. It goes without saying that you need to have an EAD to work in AOS Pending status.
You are correct. After 180 days, you will use AC21 and port to previous employer and then request USCIS for ?
Transfer of Underlying Basis? a.k.a
Interfiling. You can move from EB2 to EB3 and vice versa as you have two sets of PERM+I-140 approved by two different employers. See
Murthy article on this for more details / fine print.
Yes you are correct. That?s why I recommend my friends who are facing age-out type scenario to maintain an EB2 and EB3 I140. Whichever queue becomes ?FA? current first, you can Interfile and lock the child?s age.
Hope this helps.