not true its front wheel drive and is only 4 wheel drive when traction is lost at the front 
100% correct.
More like 10% correct. It works on a constant 90/10 distribution and sends torque to the rear based on rotational differences front->rear. It doesn't have to be 'slip'

The GTI was never rated higher, just a better value package. Overpriced, quick, tons of toys as standard, not many around.. all the qualities needed for a VW classic

(scirocco storm springs to mind)