If you want to practice individual levels of the game, it’s recommended you use the game’s cheat code system to do so. Although they are obviously not allowed in a run of this game, these can be used to warp to other worlds or minigames to practice them before a run. You can enter these by simply going to the Options Menu from the Main Menu, and clicking on the Cheat Codes button. Here is the list of all the codes useful for practicing:

Go to World 2: Y B B Y Y B → → ← A

Go to World 3: X X B B Y ↑ ↓ Y Y A

Go to World 4: B Y B Y → ↓ ← ← ↑ A

Go to the World 1 Agent P Minigame: ↑ X Y ↑ X B ↑ B X ↑

Go to the World 2 Agent P Minigame: → X Y → X B → B X ↑

Go to the World 3 Agent P Minigame: ↓ X Y ↓ X B ↓ B X ↑

Go to the World 4 Agent P Minigame: ← X Y ← X B ← B X ↑

Go to the Skateboard Course: A B Y X ↓ B A X X ↑

Go to the Spaceship Course: Y A Y A ↓ Y A X X ↑

Go to the Mine Cart Course: X X A Y ↓ A Y A X ↑

Go to the Surfboard Course: X B A Y ↓ X B A X ↑

Play the 3D Block Puzzle Minigame: Y ← B → → ← ↓ X ↓ X

Play any of the Ferb Repair Minigames: X B Y Y B → B ↓ X ↓

Play any of the Bonus Areas: Y ← Y ↓ Y Y B → X ↑