1. Do I have to apple AP if I want to come back to states when I visited China? Can I use my h1B to get in?
--better to have AP, you also can go back by applying H1 visa again, if H1 is not multiple entry.
2. In my situation, is the chance to deny my H visa really high?
--no, if you work in some key fields, it might delay you return. 140/485 has no effects on your applying H1
3. How long does it typically take to get an AP?
--2-3months