Extra dungeon 
     Clear  the  game  once and continue the new game+ file. Clear the
second Varl Mountain event to access the extra dungeon.

New game ++ 
     Finish the game in New Game + to unlock New Game ++

Unlockable:         How to Unlock:
New Game ++         Finish New Game + 

Multiplayer difficulty 

Unlockable:         How to Unlock:
Hard mode           Clear all stages once. 
Very Hard mode      Clear all stages on Hard mode.