if Eb2 I140 approval required before applying for EB3-I140 to take advantage of current PD date

[sunny123456]

i have PD for 2013 in Eb2.

Since date for EB3 have made my PD current and I can file for I485 and I140 concurrently. My perm ( under EB2) with my current employer has just got apprved and the lawyer suggested that I shoudl file for Eb2 I 140 in premium and then do downgrade on Eb3 I1 40 once thta approval comes through.

 

However I could not locate if the I 140 approval from EB2 is required ? before applying for EB3 I 140.

Followup question : I have plans to chnage employer in Jan /feb 21 and wants to gain pending I485 status ( but that would be under 180 days ) , will that help me without having me to file PERM and I140 process yet again.