First finish the game in arcade mode. When selecting Jinpachi pressing [SQUARE] get you his Dark Resurrection demon form. [TRIANGLE] gets you his normal human form. And [CIRCLE] and [X] will get you the original Tekken 5 demon form.
Beat the arcade mode 3 times and the entire stage list from Tekken 5 should then be unlocked for vs. play.
Select the Panda by pressing [CIRCLE] at the selection screen.
Choose Yoshimitsu at the select screen with [X] or [CIRCLE] for normal form, [SQUARE] for dark ninja form, or [TRIANGLE] for purple skinned ninja form.