Answer 1

The Pokemon's Nature is not really important during Gameplay. But when you are asked the set of questions in the beginning of the Game, it helps determine which Pokemon will be the Hero of the Story(In-
Game). The Pokemon you can obtain are in This Link

Answer 2

not much actually. i havnt played the game but my friend was playing it and i asked him what natures do and it just affects stat changes just like in pokemon games