You can still claim nonresident alien TAX STATUS on your tax return for this year. Please note that tax status is completely different from immigration status. Even though your will file tax return as a "US resident", you will still be a non-immigrant alien if you haven't got your GC by then.
The A# you got from your OPT EAD is one kind of "Alien Registration Number", but it is for EAD purpose only. When you get your GC in the future, you will have a new A# that is different from the one you have now.
The A# you got from your OPT EAD is one kind of "Alien Registration Number", but it is for EAD purpose only. When you get your GC in the future, you will have a new A# that is different from the one you have now.