Works as of v1.04

Step 1: Launch the game Step 2: Beat levels and get 500 berries Step 3: Enter Extra World 2 (500 berry world) Step 4: Exit to main menu Step 5: Delete save data Step 6: Start new game Step 7: After getting the first tear, exit to main menu Step 8: Continue game

As long as you've beaten all the levels, they should all be unlocked, save for World 2. You only need to do this once per game launch, but if you ever exit the game, you just need to enter the 500 berry world again.