Successfully complete the Undead Yard quest with Veemon or the Item Road quest with Dorumon.
Defeating Aprokrimon
First, destroy the five spike balls on the posts around him, avoiding the fire shots and wind blow. Whenever five flying things come to attack, just block. Do not try to jump on the area that he is on, as you will get shocked. After the spike balls are destroyed, he will shoot a purple attack that follows you. You must run around trying to hit him without getting hit. Magic and a gun weapon work well; you do not have to walk up to him, but they do smaller damage. Physical attacks are more powerful, but you must risk getting close to him.
Dorumon
Reach level 16 with Agumon.
Double Axe description
The game states that Double Axe (all types) is a bash skill weapon. However, when you use it you will gain the blunt skill.
Easy experience
In single player mode, repeat the tutorial about fifteen times, then go to Death Valley. Once there, follow a path and fight some Goburimon; do not go across the bridge. Follow the path up and fight the Goburimon. They will give 10 experience points each. Break, then get the Gate Chip, use it, and repeat. Additionally, go to Death Valley, then to the Fortress. When you are inside the guard room, defeat everyone for 32 experience points per kill. After all the doors open, go outside and enter the fortress again. This must be done two or three times to reach the next level.
Easy tech ups
After you have unlocked the "Fortress" in Death Valley, whenever you need to equip a new weapon that is too high in tech points, just return to the Fortress and fight up and down the tower multiple times. You will receive between 10 to 60 tech ups in one revolution.
Guilmon
Reach level 16 with Veemon.
Hard Mode
Finish normal mode once.
Herculeskabuterimon
Successfully complete the Undead Yard quest with Guilmon or the Item Road quest with Agumon.
Imperialdramon Fighter Mode
Complete the final side-quest, worm hole dungeon, in v. hard mode with any of the digimon.
Unlimited Items and bits
This trick requires your main Digimon as player one and any Digimon as player two. Give all your Bits to player two. Then, save player two at the Save Keeper. Next, have player two give all Bits to player one. After that, have player two quit the game at the Save Keeper, but this time without saving. Then, go to Call Keeper and have player two join in again with the same Digimon. Repeat this from the beginning until you have 9,999,999 bits, both in the bank and pocket. You can also use this trick to duplicate items. This is very useful if you want to give some rare weapons and armor to a friend.
Unlock 4th MP Move
Increase your blast technique to 1000.
Veemon
Reach level 16 with Dorumon.
Wargreymon
Successfully complete the Undead Yard quest with Agumon or the Item Road quest with Guilmon.
Weregarurumon
Successfully complete the Undead Yard quest with Dorumon or the Item Road quest with Veemon.