H1b Transfer from A-->C, B is current employer


My visa with old employer (A) is valid till May 2022. I recently changed jobs and H1 is now with B (A->B transfer). Assume, I got a opportunity with C, can I transfer my H1 from
A (still valid visa)–>C or it has to be with
B (working currently)–>C

H1B change of employer aka transfer petition happens from your current employer to the new employer. Once you leave an employer, they will withdraw your H1B with USCIS so it is no more considered valid.

Thank you. I have stamping with old employer ‘A’ and its valid till May 2022. If I go to India, should I go for dropbox (visa for B) or can I travel back with A’s visa, since its valid.