H1b multiple sponsors

[np321]

I had two potential employers filing h1 for me this year,
One of the H1 is approved and i'm planning to join this employer.
2nd h1 is still in progress. I am planning to ask 2nd employer to revoke it.. not sure if he agrees.

some queries
- what happens if 2nd employer doesn't revoke it and it gets approved. Can i still work with 1st employer h1?
- do i have to do any specific steps with 2nd h1, so that it doesn't create problem in future. like while stamping at consulate in india?
- when the 2nd h1 will get invalidated?

Thanks