Regarding child safety seats and seatbelts in passenger cars, which of the following practices is strictly dangerous and PROHIBITED by safety regulations?

1. Installing a forward-facing child safety seat in the rear row using ISOFIX anchors
2. Ensuring all adult rear-seat passengers wear three-point seatbelts
3. Adjusting the driver seatbelt shoulder anchor so the belt rests across the clavicle
4. Installing a rear-facing infant safety seat in the front passenger seat with an active frontal airbag enabled (副驾驶开启气囊放置后向儿童座椅)