1. Forest's Curse and Trick-or-Treat, two new moves from Generation VI, adds the Grass- or Ghost-types to a Pokémon. This makes single-typed Pokémon dual-typed, and dual-typed Pokémon triple-typed.
So says Serebii.(Of course, since you have Pokémon X/Y, you could do research on whether that is true.)
2. Correct.
I'll let Shane ask questions 3 and 4.