Veritas 8C is an onboard system so no other control box.
You will not be able to disconnect it without making some noise.
Need ladders to get in the outside to decommission the system completely.
You have an intermittent tamper issue, you could get someone in to diagnose and repair the issue if you would use it.
If you have no intention to use it at all then have it decommissioned for the sake of your neighbours as they need regular maintenance to be reliable.
Power cuts shouldn't trigger any alarm system, any that activate during a power cut shows they are faulty and require servicing.
These panels are known for slight transformer buzz, can happen if they are mounted to a wall that's not flat resonates through the plastic case.