F1(Expired)-H4+EAD(pending)- H1 lottery selected

Hi , My spouse STEM OPT expired on June-28- 2020 .so I have applied for H4+EAD in the 2nd week of June and received the receipt before June 28. We have been waiting for the H4 biometric since then. Her previous employer have filed a H1B application in 2021 and it got picked up in the lottery and they are ready to do premium processing .

  1. what happens if her h1 gets approved before H4 biometric? I assume we will withdraw H4 petition ? would my spouse be in valid status and what would be her status from date of H1b approval to Oct1? Can she start working from October 1 without leaving the country assuming H1B petition filed with COS?
  2. What happens if her h1 gets approved after H4 biometrics and before H4 gets approved and later h4 gets approved after H1B approval?
  3. what happens if she receives a biometric appointment after filing H1b in premium? Is it advisable to reschedule the biometric so that h1B get approved before next biometric appointment. I have seen few cases where once biometric is given USCIS will process H4+EAD even though an withdrawal application is sent for H4 post H1 approval.

what would be the best approach to maintain the right status? Please advise.