h4 stamped, on h1b not stamped

[niil]

Gurus,

here is my situation.

I came to the US on H4 stamped.

in US i got my H1b but never left US so H1B is not stamped.

I have recently lost my job and will be applying for change of status from H1 to H4 within US.

My question is, is the H4 visa stamped on my passport well until 2013 still valid?

I am planning to leave US for India and come back a month later, will it be of any problem for me to re enter on same H4 Visa?

Please help me

Thank you