1: To get to the next peak you only have to choose either freestyle or
race and beat everything in that category.

2: To earn cheat character skins you have to go to a lodge and enter the
character description screen. once there go to rewards and select cheat
characters. Then you can see how to earn them and you can buy some of
them.

3: If your friend has a memory card with a character he wants to use but
you want to use your character you can. First you go to multiplayer then
select your character. Once you are done with that take out your memory
card and put in your friends. Then press O and load his file. Me and my
brother this all the time.