The Cheat Gnome has to be entered first! Activate the gnome, and it allows you to activate the rest of the cheats after you enter them. Enter all of the cheats when pausing the game:

Cheat Gnome
L1, R1, Up, X, R2

Set Skill Level
Triangle, Circle, Square, R2, Left

Advance clock 6 hrs.
Circle, Square, L1, Up, Down

Unlock All Lots
Circle, L2, Left, Circle, Up, Circle

Give Money (9,999)
R1, L1, R2, Right, Left

Fill All Motives
Up, Circle, Up, Right, L2

Unlock All Recipes
R2, Square, Up, Down, Right, X

Unlock All Clothing
Square, R2, Down, Right, Square

Unlock all objects
L2, Circle, Down, Left, Up

Horn Audio
R1, L1, R1, L1, Triangle