This trick works for any Battle game mode. Immediately before the battle game starts, when "Ready" appears, use the C-stick to change the angle of the field. You can't do this after the game starts.
To unlock mini game mode beat the game (level 6)
Win any match in Battle mode, then replay the same match without changing any other options [except for the stage, if desired]. You'll play as Golden Bomber during the replay.
Play as Max in Battle Mode
Once you earn all Lightning Cards in Normal Mode, go to the character select screenin Battle Mode. Press Z to play as Max (instead of Bomberman).
To unlock a Mini-Game option at the title screen, complete Level 4-3.
Unlock Options in Battle Mode
To unlock a new set of options, beat Normal Mode once. At the Battle Mode stage select screen, Group A (standard power-ups) and Group B (special power-ups) options will appear.
Complete Normal Mode once. You will unlock a new option called Group A/B that is accessible during the stage select screen in Battle Mode. Press up or down to toggle between Group A and B. Group A gives you access to the basic powerups during standard Battle Mode matches, while Group B gives you access to the more advanced powerups.