- has sideways-facing seats?
There's no legal requirement to fit seat belts in sideways-facing seats. The human body bends forward from the waist - not sideways - the potential for internal and spinal injury is high if a passenger uses a seat belt in a sideways-facing seat. For similar reasons, the type-approval standard for child seats and boosters does not include fixing them in a sideways-facing seat.
A child who is required to use a child seat/booster (ie, all those under 135 cms tall who are also under 12 years old) cannot travel in a sideways-facing seat. A child who needs to use a child seat or booster must use a forward or rear-facing seat.