Digimon World 4 (known as Digimon World X in Japan) is the second Digimon video game on PlayStation 2, GameCube and Xbox game consoles simultaneously. The game was discontinued due to lack of sales. Instead of being a standard RPG like the previous Digimon games, Digimon World 4 has hack and slash gameplay and supports up to four players. The game offers a choice of one of four starter Digimon: Dorumon, Veemon, Guilmon, and Agumon. They are each new members of the "D.S.G. (Digital Security Guard)." Based on Digital Monster X-Evolution, it is immediately revealed that a computer virus known as the "X-virus" is spreading quickly and is infecting many Digimon.

"The Yamato Server" has disappeared and a new server known as "The Doom Server" has taken its place. When the first few sections of Level 1 are completed the player finds out that The Doom Server may in fact be The Yamato Server. The player is then sent to destroy the "Doom Dome." This is where the first real boss appears, Apokarimon. There is no difference between each game system, except for the graphics.

Unlockables

Game Modes
Unlocking of game modes is applicable to the first player/team leader only. To unlock it for the other players (second to forth players), you must switch the first player with one of the other players.

Hard Mode - Beat Normal Mode once and restart your game.

Super Hard Mode - Beat Hard Mode once and restart your game.

Imperaildramon PM.
To unlock Imperaildramon PM., you must beat Wamu Platform (Wormhole) Dungeon in Super Hard Mode.

Unlockable Digivolutions
To unlock the following digivolutions, you need to reach level 16 and speak to the DigiLab attendant to unlock the Digivolve technique

Agumon - Let Guilmon reach level 16

Dorumon - Let Agumon reach level 16

Guilmon - Let Veemon reach level 16

Veemon - Let Dorumon reach level 16

Unlocking Ultimate and Mega level digimon in Normal Mode
Most of these are done by completing side quests. The rules for these side quests are given in the game and by completing them you get a digivolution.

Clavisangemon - Complete Undead Yard with Veemon

Clavisangemon - Complete Item Road with Dorumon

Herculeskabuterimon - Complete Undead Yard with Guilmon

Herculeskabuterimon - Complete Item Road with Agumon

Wargreymon - Complete Undead Yard with Agumon

Wargreymon - Complete Item Road with Guilmon

Weregarurumon - Complete Undead Yard with Dorumon

Weregarurumon - Complete Item Road with Veemon

Glitches

Duplicate Items, Bits, etc.
First off, you need to have at least 1 bit or item. This works well if you've picked up a weapon in the beginning of the game with many mod slots, which can be sold for a lot of bits. Next, you need to load up your game and log-in with that Digimon, but don't start the game. Instead, jack in another controller (taking your current controller out and putting it in another controller slot works) and create a new Digimon.

Now start game and give the items or the amount of bits you want to duplicate to the new Digimon you have just created. Go to the save menu and save the game with the second Digimon only in another save slot. Now shut off your game and reboot with both Digimon again. Your second Digimon should have the item, but your original Digimon won't lose it. This can be done as many times as you want.

Here's the final boss battle: