f1 and i485 pending

Thanks so much xiaobaitu for your help!

A followup on phd student while i485 pending (co-applicant). My f1 status is off due to traveling abroad while i485 pending. so now I only have i485 pending and EAD/AP.

Q1: If i got a job offer before the i485 approves, how could I transfer to h1b - do i must turn back to china for the transferring?

Q2: if my i485 was rejected and I got a job offer, what would be the best way to handle that?

Thanks a lot and really appreciate your help!