(1) Do I need get a new I-20 before I leave for China?
- No.
When you come back, you are no longer an F-1 student any more.
(2) If not, what else from the office of international students are needed?
- Nothing
(3) What other documentations do I need for the travel,except the AP, 485 receipt, I-94, and passport?
- Just AP and passport