再请教I-824. 比较麻烦。What should I do?

Background:

I have NIW I-485 pending name checking for almost 3 years. I have done everything except for WOM. I have used AP twice in the past year (2006.12, 2007.6) and stayed in China for about 3 months each time. I will go back to China again within a month, and have to stay for 5 months or so. I believe I can't use my AP to come back (right?), so I plan to submit I-824 for consulate process, and apply for H1 visa when I come back (My H1 is still valid and I can always get a new one). I thought there is not an approval issue of I-824 in this case and I can just submit and leave, but I was wrong after getting Xiaobaitu's answers. I have only about 1 month in the US, but it takes 6 months to process I-824.

I have to leave, but just want to know if there is still a way to keep my pending I-485 valid.

Thanks a lot.


Questions:

1. Before I-824 is approved, can I still use AP to come back in case of an
emergency, e.g., a RFE on the I-824?

2. If there is no RFE, are there any other risks on my I-485 if I leave US
before I-824 is approved?

3. What will happen if my I-485 is approved before I-824 is approved?