H1b transfer after expiration

My h1b expired in Sep 17. Current employer (employer 1) filed extension 2 months back and I got a RFE 2 weeks back.
In the meanwhile I got a job with employer 2 and they are ready to file transfer.
Can it be done? If so what are the implications?

  1. What if employer 1 petition gets denied before employer 2 petition decision comes through?
  2. What if employer 2 petition is approved first? Do I get a valid I94? If not will I be able to get it stamped in Canada for example?