The car alarm keeps going off, randomly/I have removed the fuse that should have been responsible for powering the car alarm What do I do? How can I physically disconnect the alarm?

actually if you look just inside your door on the center piller there should be a button behind your seat belt hold it for 3 seconds each time you go to lock the car. when you push it the light on your door lock will light up then go out this will turn off your cars motion detection in the interior of the car. my cars alarm does this all the time as well and i find turning off the motion sensors stops the problem. and as for the water problem well my guess is your car sucked up water into the intake and flushing the system means they purged the water from your engine. this is the main reason off road vehicles have snorkels to keep the water out of the intake or exaust

The boot/truck light switch is the answer. It's the blue micro switch on the top of the latch. It probably has water in the plug that pushes in the top. Its blue also. Once you unplug it you will notice the boot light will no longer work or show up as open on the dash warning system. The switch maybe fine as the way its wired up does not allow water or damp to travel from the plug to the switch. It maybe as simple as a clean up of the dirt or just leave it disconnected. Only words of warning if your A4 is a convertible just make sure the boot lid is closed before opening the roof as the roof hatch and bit lid use the same space when open and will hit. It's not hard just turn around and look.