Yes, it can be mounted on a wall in the vertical position
I have had mine for three years and used them for hobbies and such. I keep all my batteries on charge all the time and it has not affected them at all. It charges back to full and moves on to the next battery. Great charger.
That rotates the charge cycle of batteries
Yes it is
I left mine plugged in for well over a year without any experiencing any problems from my batteries. Sometimes I used them regularly and other times it would be weeks before doing so again. Each battery functioned perfectly. So I hope this helps you Jim.
Yes. It will charge any 18 volt battery.
Yes. It will charge any 18vt. battery made by Milwaukee.