need info for AP going back to China, Thanks

1, when leaving, at LAX, I should turn in I-94, I have the original F1 one and a newer Hib one, which one to turn in? or both??

2, when come back, at Shanghai airport, what do I need to show beside AP, to get on the plane?

3, How long does it take for AP to get through immigration, when I come back, 1 hr or 2 hr? Since I need to catch a train.

I understand since I am coming back to the same position, my H1B is still valid until next renew, right?

Thank you in advance!