I am still a Ph.D. Candidate student, my I-20 expires in about 2-3 yrs.
I just started working full time a couple of months ago, so I got my H1b now. If I were to go back to China, should I use my H1b visa?
-You shoul get the H1 visa if you want to work after you return.
What about my I-20 and F1 visa?
-It has been invalid after you changed your status from F1 to H1.
How possibly can I use it in the future?
-No. If you wan to get back to F1, you need to ask the school to issue a new I-20 and get a new F1 visa outsie US or change H1 to F1 within US. However, you can continue your study with H1 status as a part-time stuent.
Do i need to contact the international office in my school for a new copy of I-20?
-Only if you want to get back to F1 student, then can you do that and get the F1 visa in China this time or in the future.