H1 B holder in India wants to convert to H4.

i have valid H1 and I want to join my husband in US on H4.

If I convert my H1 to H4 and travel US,will my H1 be still valid.

And in the mean time while in US, if I get a job , how diffcult it will be to convert H4 back to H1, for the same employer or different employer.

If I resign and join my husband will my H1 be still valid, as If I am going on to US after taking a vacation from my present employer.

Any help on these questions is highly appreciated.