We bought the seat recently; I would say that the seat can be fitted with the belt when facing = driving direction. Backwards it doesn't look like it in my opinion. With Isofix so far a great child seat ;).

As I understand the instructions, yes. Under the following conditions:
Backward facing only for children in group 0+.
Forward facing only for group 1 children.
For group 2 / 3 a belt installation is not mentioned because the belt is only used to secure the child directly and the seat is attached to the car by means of an isofix.