scantronic 8000 bf fault replacing battery?

This afternoon internal alarm has been going off every few minutes. Stops when put the code in and goes off again. Has been going off for a few days but not as frequently.
Looking on this forum, seems I need to replace the battery in the control panel. I opened it up to see which battery and the external alarm went off and a tamper error code came up. I put the screws back in and put in the code and the alarm has been quiet for the last hour.

looking on the forum I see I need a Yusa 7 amp battery - i cant get it till tomorrow if I can get it in a shop or for a couple of day f I have to order.

My question is - if the alarm goes off at the night and keeps going every few minutes, will taking the battery out and killing power stop it? And when I finally put in a new battery, will the old code still work? - I have no other codes or is there a default engineer's code that I need to put in?

Many thanks.
Joe