My H1 visa kicked off on October 1, 2019 (not stamped yet). I received a new offer and initiating H1 transfer. Let’s say if the transfer is approved but I have not started employment yet. Can I go in January and get it stamped on my old H1B approved petition ?
Technically you can, as long as you continue to work for the old employer. You need to use the same to come back to US and work for the same old employer.