a confusing H-1b/RIR question

I am working at company A under H-1b and have only 2 years left, now company B is sponsoring me for GC and preparing RIR petition for me, my question:
1)what if I did not get the LC at the end of the 6th year of H-1b, can I apply for extension and still work for A while waiting for the approval for B?
(P.S. B is the parent company of A and has office in other state which is quicker in LC processing.)