H1B transfer while extension in process and existing petition expired


I am on H1B for company A, current petition expired (stamp as well) and extension is in process.

Now, If I have to transfer my Visa to employer B.

Will the visa transfer be based on extension filed by company AWhat are the chances for either get rejectedIf extension gets denied or RFE, can the transfer be still successful and validCan company B create request for transfer and extension togetherCan I start working for company B once I have receipt number for transfer requestAppreciate any help with answers and any extra knowledge in this situation.