In order to change the address on 485, you have to send a letter to INS to request a change of address on your 485 application.
AR-11 got nothing to do with address on 485. All the Immigrants including Green Card holders need to file a AR-11 whenever their physical address changes to notify the INS.
I did changed the address on my 485 application. My Attorney sent a letter to request to the change of address on my 485 application. After 4/5 weeks I called TSC to confirm the change of address and it was changed.
When I changed address on my 485, I used my cousin address as he is not going to move from that address in near future. I filed a AR-11 to notify my physical address whcih in different state.
I hope the info helps.