If you search (put GPS in double quotes - "GPS") you will find many threads about it.

Depends on the airline if they allow it or not, some do and some don't. None allow it at takeoff and landing.

You need to be up against the window for it to work, and even then I'm probably less then 1 in five times that it works. But yes, there is a chance you will lock onto a signal if you keep trying.