Travel with AP Questions. Help! Many Thanks!

I am planning to visit China on my AP for an urgent family matter. Here are a few question regarding using AP to travel.

1. Since I've already had the interview for my 485 petition -- currently the case is pending on name check, my I-94 was collected away by the USCIS officer in the interview. So in my case, I will not have anything to turn in when I leave the US. Will this possibly become a problem?

2. Since I do not have a I-94 card to turn it, how the USCIS know when I leave the US? Or will this be a matter at all?

3. What documents besides AP and passport do I need to re-enter the US? 485 receipt? The interview paper from the USCIS interviewer?

4. I have two AP copies. Do I need bring both of them with me?

Thank you so much for sharing your knowledge and experiences.