All Monsters:
When you are at the Soulin Monster Ranch, goto the "Options Screen" and highlight "Buy Monster": Then press the following:
R2, R1, L2, L1, R1, R2, L1, L2, L2

All Items:
Goto the "Options Screen" and enter the following:
R2, L1, R1, L2, R2, L1, R1, L2, L2

View Ending:
Goto the "Title Screen" and enter the following:
L2, R1, L1, R2, L2, R1, L1, R2, R2