I am into 7th year of my H1B, with company "A". H1B extended for 3 years based on I-140 approval & valid upto 9/2013. Priority date in 05/2008. I-140 approved under EB-3. I-485 not filed yet.

I have 4 year Engg degree from India. Working in same field of work for co."A" from 2004 ... 1 yr in Europe, 5 yrs in US.Am now planning to transfer my H1B to company "B", & proceed my Green-Card process by porting to EB-2.

a) At this point, can I transfer my H1B, even though 6-year limit has passed?
b) What documents do I need to get from co. "A" to proceed my GC, using current priority-date ? Are there any ways co. "A" can stop my GC - by revoking H1B or approved I-140?
c) How can co. "B" file for my GC under EB-2 ? Can I show the experience I have with co. "A" here in US ?
Thanks.