How early can one apply for H4-to-H1B?

[telecom]

My spouse would be joining IM residency program in June end on H-1B visa. She plans to go to India in March end and return May 10.

1. When can she apply for the H-1B visa?
2. Is it okay for her to apply through premium processing in February and then once she gets the approval go to India and get the visa stamped.
3. How early can you get the visa stamped and not join the job after entering US?
Thanks in advance for your prompt response!

 

[jaxen]

1. 3 to 6 months after coming into US, one can apply for change of status
2. If condition above is met, yes. Dont forget consular notification
3. Should join the job pretty soon. INS uses 60 days as a measure of intent.