1) yes, i did it before, but need a lot of explain the reason, s

2) not necessary, call for reschedule is pretty simple.

probably you forgot fill the form following the on-line AC-11. i missed it too at first time. you can refill AC-11 again and continue to fill the forms for changing i485 address. you can call for changing address but sometime it doesn't work too, you should go to local office directly to double check if your address is changed or directly ask IO to change your address.