User Manual GE APWA14YZMW Portable Air Conditioner

There small holes in the panel where you could probably
screw into you window frame, but I wouldn't trust that to
keep intruders out. It's probably more prudent to add
hardware to your window so the window cannot be
raised should someone try to break or kick in the panel.
We use our unit in a room only while we're awake. When
we're done for the day, we remove the panel and lock
the window until we need to use it again.

Yes, it can. The window mounting panels included with
the unit will fit an opening from 20" - 46". In a sliding
windows, the mounting panels are mounted vertically
instead of horizontally.
The installation instructions provided with the unit
provides the directions you need to do so.