To unlock cheat mode, go to the "Options" menu at Anthony's house and select "???". Select the lights in the correct order. Activate the following cheats by entering the corresponding codes:

CHEAT FUNCTION - CHEAT CODE
Mirror mode - [Right Arrow] [Left Arrow] [Left Arrow] [Right Arrow], then Ladybug, Clover, Boy Face, Plane, Bus, Bike. Then, while selecting a stage in Free mode, press 2 to play the mirrored version.
Master Higgins Ball - [Right Arrow] [Left Arrow] [Left Arrow] [Right Arrow], then Square Robot Face, Car, Award Ribbon, Bike, Helicopter, Strawberry.

Unlock the following marbles by performing the corresponding tasks:

MARBLE - HOW TO UNLOCK
Anglerfish - Beat Challenge Stage 11 in the Sunken Depths in Normal mode.
Baseball - Get 30 Gold trophies in Easy mode.
Bomb - Get 20 Gold trophies in Normal mode.
Broken Television - Get 35 Gold trophies in Normal mode.
Dog - Get a Gold trophy in Easy mode.
Earth - Beat Challenge Stage 11 in the Space Station in Normal mode.
Egg - Get 16 Gold trophies in Normal mode.
Figure Roller - Beat Stage 10 in the Stump Temple in Normal mode.
Football - Get 20 Gold trophies in Easy mode.
Frog - Get 8 Gold trophies in Normal mode.
Goldfish Bowl - Get 12 Gold trophies in Normal mode.
Hedgehog - Get 40 Gold trophies in Normal mode.
Panda - Beat Stage 1-1 in more than three minutes.
Penguin - Get 5 Gold trophies in Normal mode.
Pig - Get 3 Gold trophies in Normal mode.
Saturn - Get 30 Gold trophies in Normal mode.
UFO - Get 25 Gold trophies in Normal mode.

To unlock Hard difficulty, beat the game on Normal difficulty.

To unlock a free recipe, at the menu screen click on the ant when it's behind the World Map dandelion.

Unlock the following characters by performing the corresponding tasks:

CHARACTER - HOW TO UNLOCK
Bomberman - Get 40 Platinum trophies in Hard mode.
Easter - Get 35 Gold trophies in Hard mode.
Martian - Get 25 Gold trophies in Hard mode.
Master - Beat Hard mode.
Monster - Get 30 Gold trophies in Hard mode.
Paper Bag - Get 15 Gold trophies in Hard mode.
Pumpkin: Get 10 Gold trophies in Hard mode.
Snowman: Get 5 Gold trophies in Hard mode.
Space Suit - Get 20 Gold trophies in Hard mode.