H1B Transfer Question

[visaseeker8567]

In the year 2018 , I was on F1 Stem OPT .I was working for company A during my OPT and they have sponsored me for H1B visa . I got another offer from company B and even they sponsored me an H1b visa as a future employee of the company . Both petitions got picked in the 2018 lottery and company B got its H1B approval on June 30th ,2018 with validity for 3 years where as company A petition was still in processing state until October 1st 2018. I waited eagerly until October 1st 2018 for the visa approval of company A. But due to the delay in processing's I didn't get approval of company A by October 1st 2018.  Unfortunately I haven't joined the company B and continued my employment with company A since they have used my approved company B  petition and filed the H1B transfer petition on October 1st, 2018 with the start date as October 3rd,2018. Recently ,I have received an RFE asking me how I maintained the status on those three days i.e. Oct 1-3, 2018 .  Any suggestions to answer this RFE to get my transfer approved? If in worst transfer decision is not in my favour, can I go and start working for company B If they have an offer for me since they haven't revoked my H1B petition yet?

Edited May 8, 2019 by visaseeker8567

[gopalakrishnach]

I am not sure but i guess there a time limit on companies must report to USCIS once an H1B is approved and the employer is no more working. I might be wrong. If I am wrong and your Employer B did not revoked H1B you can work with them...