random question about factory radio

on most cars the radio turns off when you turn the key back to a certain point. right?
ok my 2000 cavalier radio turns off once my door opens, it doesnt do anything when i turn the key. i dont know. maybe its nothing but i would like to know if this is the way its supposed to be in this car.

also, this is not a big deal but im interested...
a friend was in my back seat and he was messing with the seatbelt and he broke that little plastic seat belt guide off the elastic strap. anyone know where i can get another one? its a small thing but it bugs the crap out of me to know that its there.

thanks.

That Is Normal With The Radio, And The Piece For The Seat Belt Go To A Junk Yard Or Take The Other One Off