Approved labor and i-140 from company A
Currently working for COmpany B on H1(7th year),havent started GC process yet
Priority date is current in Jan-2012 bulletin.
Company A want to file for I-485 only after coming back to their payroll.


Question:
1)As greencard is for future employment, is it really a requirement to be on sponsored company(A) payroll to file for I-485?
4)What are the options i have to stay with company B and still can continue 485 process with company A?
5)company B is offering me to take unpaid leave for 6months and go back to company A to complete the rest of GC process.
Is it legally possible. Is it possible to be an employee of 2 companies on H1.