H1b to H4 Change of Status

[PThukral]

I and my wife are working in the US on our individual H1b visa (valid for another year). Both visas and i94s are valid for another year or so. My wife's project assignment may end soon and the employer is expecting her to return to our home country at the end of the assignment. Assuming that she goes on unpaid leave or quits the job, can she stay on H1b while not being paid or while not working. If no, then please advise

the process of change of status from H1b to H4

Within what duration does the change of status have to be filed to avoid being "out of status"

At what stage should the change of status be applied

the typical time taken for the processing