Dependent VISA for H1B Extension

My VISA will expire on 1 Oct 2014 and I have filed extension on 22 Sept 2014. I have following queries regarding extension and dependent VISA

  1. How many days can I stay in US after filling H1B Extension?
  2. How many days it will take for extension approval?
  3. My wife is in India and I need to Stamp her VISA. In my case when I can stamp her VISA?

Any help will be appreciated

Thanks and Regards,