2.Because clause should be subjunctive mood since Parliament did not so practically.
3.The gerund which denotes statement of actions is preferrable to the infinitive which denotes some purposes by the actions. The structure of sentence can be it ... to do when you use the infinitive to do to be the real subject while it be the formal subject.
But in oral English, we usually say the sentence Don't do that. So I think this question gives us a tip of ETS's rule that just so can be used to refer a verb in GMAT.