H1b transfer while pending extension

[bvnsin]

I'm on H1B with employer A working at client place B. My employer A filed extension under normal processing on July and my i94 got expired on August.

Questions:

can employer B(client) file h1b transfer under premium processing? If so will it be considered as bridge petition?

If employer B h1b transfer approved do I need to exit and return?

Should I upgrade employer A extension to premium before doing the transfer? Is that better option?

Any other complications?

Please advise.