No Title:
Enjoy the original, stand-alone Sonic & Knuckles.

Sonic The Hedgehog:
Play new layouts of the Special Stages from Sonic The Hedgehog 3 and Sonic & Knuckles. Press , , and (, , and for Classic Controller) simultaneously to display the Menu Screen, and press to start the game. Once a Stage has been completed the next Stage will automatically begin.

Note: Special Stages can be accessed by entering codes on the menu screen. These codes are displayed at the end of each Stage.

Sonic The Hedgehog 2:
Play through every Stage in Sonic The Hedgehog 2 with Knuckles.

Note: Sonic and Tails can not be used.

Sonic The Hedgehog 3:
Enjoy the complete scenario, starting from the very beginning of Sonic The Hedgehog 3 and continuing right on to Sonic & Knuckles. Not only can you play as Knuckles for the entirety of both games, but it is also possible to play through as Sonic and Tails (just like Sonic The Hedgehog 3) and save after each Zone.

Note: Save data from Sonic The Hedgehog 3 will not be carried across when locked on to Sonic & Knuckles.

Note: The Lock-on System is only compatible with Sonic The Hedgehog 1, 2, or 3. No other game will react to the Lock-on System (this includes Sonic The Hedgehog games on other platforms). Once you choose a game to Lock-on with, the game will automatically reset.