H1B Visa Transfer

I was employed by company A on H1B and got released from A June 2nd week, got a new offer from company B in May 2014 and Company B filed for a H1B transfer, which got approved June 1st week. 1st week of June, I received another offer from Company C, which I really want to join.

1) If I dont join Company B and wait for company C, will not be I out of status till the joining date of C?

2) Considering I have approved petition from B, leaving it and waiting for joining C wouldn't be a risk, being C has just initiated the H1B transfer process?

3) Should I join B and tell C to process my Visa transfer and I will join after a month been worked for B, and till that time petition will also be approved from C?