Urgent Help: Question about AP

Please help:
I got my AP and plan to use it, but I have the following questions:
I am using OPT now, and my university is going to apply for H1b visa for me, which may take a long time. So if I go back to China and return to my university:
1: Can I still work for the same univerity?
2: or do I need apply for EAD or H1b again in order to work?
3: Can I still use my OPT until it expires?
4: Do I have to wait for the H1b to be approved before I go back to China?
5: Is there any problem for H1b visa transfter in future if I used the AP?
My case is EB2 NIW with 140 approved, I did not apply for EAD.
Thanks a lot for your help.