H1b Visa Petition Expiry date 2015 is 1 Year

USA H1B Visa
1

Hi,

My H1b Petition is approved with expiry date as 30Sept2015. Few Questions i have:

  1. Will my visa be valid for a date not more then Petition Date?

  2. Once i am in US, and my Petition Expiry date is approaching, do i have to come back to India for Visa and Extension or the same can be done from USA only?

  3. Is there a time limit till when i should get my stamping done before petition expires?

Please help me with this.; Really tensed.