At the load/save screen, press Square, Up, R1, Triangle, Down, Select to choose a starting level on the normal difficulty setting. Press R1(2), L1(2), Square, Left, Triangle, Circle at that screen to choose a starting level on the hard difficulty setting. Note: Only previously completed levels may be accessed.
Bonus shop items
At the shop screen, press R1, Down, L1, Up, Square, X.