H1B visa extention without travelling to USA

Here’s my situation:

I have H1B petition approved and it is valid from Nov 28, 2014 till Sept 30 ,2015.My employer
says currently there is no opportunity for me in US. So I need helping hand to check on my below
questions. (Please note I am in bond with my current employer until FEB 2016. So
I can’t find another employer too):

  1. How soon My current employer can file extention for me ? And what would be the $ amount they have to pay for same ?
  2. Is that the thing , I have to go again for Visa interview again once I get extention (As I have’t flyed to US)?
  3. Is there any deniel case for above sitaution when going for extention without flying to US?
  4.   What all issues I could get during this extention (In my case) ?