my h1b applied in 2017-approved after RFE submission-but petition revoked by employer after that

Hi, my H1B application was selected in Apr 2017 lottery and my employer received approved form I-797 after submitting RFE for my case. After few days when i checked in USCIS site i came to know that application was revoked on employer’s request. When i asked the employer they told me by mistake it happened and they will re-approach the attorny. they are not sharing the soft copy. So i have few questions.

  1. Does the I-797 approved form has any validity period with in which i need to either transfer my H1B to a new employer or reapply through same employer?
  2. If my employer is not willing to reapply, Can i transfer that to a new employer? what is the process.
  3. Is my employer has the rights to cancel my H1B, If he is unwilling to allow transfer?