There are a total of twelve maps in any mode that you have to complete. To know whether you've completed them all, check to see if Boss Rush is unlocked in the mode, as it is a present box in the middle of the screen only obtainable when this has been satisfied. Keep to using one character per mode, as there are two reasons to play: unlocking their intro and finale videos, which are shown through a gallery option from the main menu, as well as their personal weapon to be used by others.