Ok, i understand the basic functions and what zones the key needs to be in to do what. I even found out once you start the car, you can get out of the car and as long as the key is on you you can even lock the doors.

Since it's 15 degrees out now, i've done this a few times. I'll run into my house, but lock the doors and keep the car running (which is technically ticketable but anyway)

At what point does the car cease to function without the key? Can i get out of the car, let my girlfriend hop in the drivers seat and she can drive off even if i forget the key in my pocket?

What if i'm getting gas and someone hops in my car and drives off but the key is still in my pocket?

Or dies it just run until someone turns the car off?

I was told that it will run until you turn it off if you don't have the key, but I have never tried it.