AC-21 Portability - Help needed


Registered Users (C)
My friend had filed his labor in 2002 june with company A in EB2 category(Have Masters Degree). Joined company B and filed another labor in EB3 category in (2004) in different Immigration center.
Company B labor / 140 got cleared (180 days completed for 140) and 485 is pending for more than 1 yrs in EB3 Category.

Question 1) If he shifts :confused: to company A using AC-21 can he use EB2 labor priority date of June 2002 (Cleared in 2004 and probably used by other employee) with current I-485.

2) If yes , will there be any issue while changing centers.

3)Which skills set :confused: should he use after moving to company A using AC-21 - first or second labor.

Regards & Advance thanks for your inputs.