Yes on #1 -- the strap is for a child safety seat.

My 2 1/2 year old loves to ride "Daddy's red sports car," and we have a car seat for him that uses the LATCH system. There are two hooks inside the void between the seat-bottom and seat-back for hooking the car seat, and there's one on the back of the seat for the third LATCH anchor.

The strap is to keep the long belt for that third anchor from sliding off the top of the seat in either direction.

Please note: always turn off the airbag before putting a car seat in there!

I used to have an FJ Cruiser with a scale built into the passenger seat that would disarm the airbag if a certain weight range was detected. Unfortunately, anything left in the passenger seat (12 pack of Pepsi, briefcase) would set off the seatbelt warning beep. Annoying!