First off, you need to have at least 1 bit or item. This works well if you've picked up a weapon in the begining of the game with many mod slots, which can be sold for alot 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 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.
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.
To unlock Imperaildramon PM., you must beat Wamu Platform (Wormhole) Dungeon in Super Hard Mode.
To unlock the following digivolutions, you need to reach level 16 and speak to the DigiLab attendant to unlock the Digivolve technique
Most of these are done by completeing side quest. The rules for these side quest are given in the game and by completeing them you get a digivolution.