When you're defeated and the continue screen appears, press the start button repeadedly.
Stage Select
On the game start screen, press X, Select, A, Select, Y, A, X and Select. Use the L and R buttons to scroll the list.
Begin on level 6
On the game start screen, press A, X, A, Y, A, X, Slect, Start, and Start.
Original Pitfall
Entire original version of Pitfall is hidden in this pak. To find it, at the start game screen, press A, A, A, A, A, A, Select, and Start