Enter RT, X, LT, Down, Right, LB, LT, RT, Y, [X] as a code at the "Cheat Codes" screen under the options menu to unlock all sleds.
Choose "Options" from the main menu, then select "Cheat Codes" and enter the following: X, Y, Up, Left, LB, LB, RT, X, Y, LT
Choose "Options" from the main menu, then select "Cheat Codes" and enter the following: LB, RT, Y, UP, DOWN, X, LT, LEFT, RB, RT
Here are the various achievements that can be unlocked in Amped 3 and added to your gamerscore.
VIVA VALLE!: Impress the required amount of bystanders in Valle Nevado
Vamonos a South America: Finish Act 2 of the story
Snowmobiler Merit Badge: Travel 10+ kilometers on a snowmobile.
Snowbird Dawg: Impress the required amount of bystanders in Snowbird
Snowbird Bound!: Finish Act 1 of the story
Sledding Merit Badge: Earn 1,000,000+ points in sledding scores.
Reunited... And It Feels So Good (100): Finish act 4 of the story.
Rescued Weiner Boy!: Finish Act 3 of the story
Park Designer Merit Badge: Build 200+ terrain park objects.
Northstar Nirvana: Impress the required amount of bystanders in Northstar
Lesser Snow God: Get a medal on every challenge
Laax Stock & Barrel: Impress the required amount of bystanders in Laax
King of the Mountain Lab: Impress the required amount of bystanders in DC
Greater Snow God: Get a gold medal on ever challenge
Big Musical Finale (100): Defeat Baron
Get the indicated number of points in a combo to unlock the corresponding item in Park Builder mode:
Lighthouse: 1,000,000 points
Helicopter: 800,000 points
Go to the cheats menu from the options screen and press down, x, right, LB, right, RB, x, right trigger, left trigger, y.
Press Left, RT, LB, RT, X(2), Y, Down, Up, [X] atthe cheats entry screen.
Enter in X(2), LB, Down, Right(2), Up, Y(2), LT atthe cheat codes menu screen.