To use cheat codes under Inazuma Eleven 3 (Nintendo 3DS), you will need the Action Replay, the famous accessory that contains thousands of cheat codes for different games. For Inazuma Eleven 3, it is possible to unlock all special moves, recruit all the characters and to spend your resources to their fullest. More specifically, you can choose a specific skill or hire any player. If you're more interested in raising your skill level and beat the game without cheating, there are online tutorials (text and video) to help you to progress.
There are some hidden teams or players that can only be unlocked through side quests. These quests are not compulsory, you can skip them if you want to complete the game more rapidly.