H1B old petition still active even he or she came on H4?

My wife is willing to come to USA on H4 visa and she already had a approved H1B petition from Indian MNC. but MNC didnt have USA project for her.

Will she come to USA on H4 dependent and if MNC didnt revoke her H1b petition will she able to transfer and convert to H1b status?

if MNC revoked her H1b did she follow cap or she can apply for H1b any time?