For added security, the door is not removable on Cannon Safes.
For added protection, Cannon Safes are not equipped with a key backup.
The size of the knockout is ½ inch and there is only one hole. Every Cannon Safe model comes with a knockout. If you decide to use it for any reason please be careful not to alter the hole in any way as it may void your warranty and damage the integrity of the safe.
This is a knockout that allows you, if you so choose, to run your own electrical through to the safe so you can use dehumidifiers or lights that require power. This does not effect fire rating, as long as the hole is not altered in any way.
No, your combination is stored within the locks computer and will not be affected if you change the battery or if the battery dies.
The knockouts are small enough that they will not be an issue if a fire event occurs. As added protection though, Stack-On offers an installation kit which includes seal that expands for extra protection.