When can I travel to usa after H1b extension from india?

Hi there,

My H1b got expired in Oct 2015 and now my company is planning for H1b extension. I am having following question on it.

  1. If company file H1b in premium processing than how long it will take for approval?

  2. After approval and stamping, can I travel immediately or I need to wait till Oct 17?

Thank you.