H1B policy and usage

My H1B was applied from a Company ‘A’ in April 2014.
My Petition was approved and I have the Receipt Number and copy of I-797B and I-797C.
It is valid until May 2017. I never got it stamped and I have never traveled to US.
a) Is it compulsory that I need to travel to US under Company ‘A’ for the first time.
b) If I leave Company A now, can I still use this Petition (visa).
c) Can I share the above details to any other Company who is willing to give me a job in US ( if yes, what is the that I/Company has to do?)

  1. No

  2. Another company will have to file cap-exempt petition for you, and submit current approval notice as reference and proof of having made through the cap. So you cannot use A’s petition for travel, but as proof for B’s approval.

  3. Yes. See (2)