Hi ,I am your old client.Here are my Q

1)During H1B transfer, what is the safest time to start working with new company.(i)after getting new H1 receipt notice?? or(ii)after new H1 approval?
2)What are the options i have if new company H1 is denied and old company H1 is revoked?
3)My I-94 is expired but there is a new I-94 at the bottom of the I-797, is it valid and am I eligible for a new H-1 transfer? Do i need to depart from US and reenter?
4)My GC 140 is approved with current employer and i am at 4 year on H1 . When i apply for H1 transfer do i get H1 for 3 years?
5)My new employer wants to file GC.It has different job duties compared to previous PERM application.Can i retain old company priority date if new company files GC? What if old company cancels my approved 140 ? Thanks.