H4 dependent to H1B transfer - Transfer Options?

My H1b extension got denied and now i am in India. My spouse has valid visa and i am planning apply H4. After change of status(h1b - h4),
What will happen to my h1 because only 2 years i have been worked in US?
After i reach US with h4, can i contact any employer to transfer my H1?
What will happen, if my h1 gets revoked by the existing employer?

Nothing, you can recapture the unused h1B. Check H1B Recapture Rule
Yes, you can do that.
No, it does not matter. Employer can only withdraw, they cannot revoke. Unless, it is revoked for fraud, you would be cap exempt for transfer.