The actual unit is 16" wide, however in order to properly install it you also need to add the wings to it as the wings are what actually screws into the window and secures the unit in place. Technically, it's probably possible to install the unit using the brackets which lock the windows in place and nothing would happen, but my guess is for liability reasons they aren't giving that advice. If the thing falls out and conks someone on the head they don't want the lawsuit.

It comes with little brackets, but I didn't use them. I cut a couple of 1"x1" boards cut to length from the top of the window down to the top of the window sill. wedged them in place. Extremely secure, can't raise the window from the inside or outside without removing the wood posts.

Yes, you can program it to whatever set point and turn the unit to auto setting, and it will control the temperature to that setting. Much like a home central heating and air unit. The fan will run, but the compressor is only running as needed to cool the air.

The unit uses a regular 110 wall socket plug. Regular prongs with a ground prong.

Slide out, on the front right side of unit.