Locksmith is, despite what the title says, not about repairing broken locks.
Level/Difficulty Select#
At the screen showing what level you are on, hold A + B + Select. While holding them, use Up/Down to change the current level and Left/Right to change the difficulty level.
Hidden Sachen Copyright#
Press A, B, B, Select, A, B, Select, B, A, Select on the title screen.