H1B transfer just before(3 months) of Visa expiry in U.S

[sagarsandy]

Hi Team,

I am working in Company A working for company B as Client. Our client B offered me to join as a full time in Company B.I am interested in joining but I am having some confusion regarding my Visa.

My Visa is going to expire on 31-Aug-2017 and Petition expiring on 31-July-2017. But still, i have not applied for the extension. In this situation can I transfer Visa to Company B?
If yes please suggest when i can join Company B?
And please let me know when i need to resign Company A?
And if Visa transfer to Company B not completed before existing Visa expires what happened? Is it out of status? In this case, i need to leave the USA?
And how many days it will take for H1B Extension and H1B transfer?

Please suggest

Thanks...