Here is full info for address change:
1 file form AR11 for address change ( it will not chage you address on pending petitions with USCIS)
2 update NCSC on 18003755283, your new address, provide them your ,WAC,EAC or LIN # of I-485 and reciept # of any pending petitions with service center, provide the receipt#, your name, DOB, A#( A# is on I-485 filing reciept)
3 write letter to service center for address change on your pending I-485( if you have spouse I-485 pending He/she also need to change address on her/his I-485 letter need to be signed by spouse with date and reciept# of pending petitions) or any pending petition with them provide your past and NEW address, attach I-485 receipt copy, write your I-485 reciept # name, DOB, A# on cover letter so that you get fingerprinting notice at your new address. Send the letter to your service center with certified return receipt and out side the envelope write in big bold letters ATTENTION: ADDRESS CHANGE for Pending Form I-485 ( or any other application).
4 if want to use AC21 THEN if the past company lawyer filed I-485 then better change your lawyer and fill up new G28 with your new lawyer and he can update USCIS that he represent you and can mail form G28 to sevice center, he can also make a request to chage your New address on Pending I-485 and he will get if any RFE, if you dont change any RFE will go to past lawyer
*** do the all 1,2,3,4