checked-no =>Stage Select: In Mushroom Hill Zone, jump and hang from a dangling vine platform. While hanging, press Lx3 Rx3 Ux3 and a tone will sound. Press <START> <A> and you'll be back on the title screen. Select a character and press <A>+<START>. Please note that this code only works for Sonic & Knuckles, and NOT for Sonic 3 & Knuckles. =>Sonic 2 & Knuckles Codes * Stage Select: On the title screen, press Ux3 Dx3 L R L R and a tone will sound. Press <A>+<START> to enter the stage select screen. * All Chaos Emeralds: On the stage select screen, play songs 01, 06, 07, 07, 07, 02, 01, 06. A tone will sound. Start the game and you'll have all the Chaos Emeralds. * Debug Mode: In the stage select screen, play songs 01, 09, 09, 04, 01, 00, 01, 08. A tone will sound. Highlight a level and press <A>+<START> to play the stage in debug mode. =>Sonic 3 & Knuckles Codes * Stage Select: In the Angel Island Zone, jump and hang from a dangling vine platform. While hanging, press Lx3 Rx3 Ux3 and a tone will sound. Press <START> <A> to return to the title screen. Choose the new Sound Test option to enter the stage select screen. * Debug Mode: Use the stage select code to enter the Mushroom Hill Zone. There, grab a dangling platform and press Lx3 Rx3 Ux3 and a tone will sound. Press <A>+<START> to return to the title screen, enter the stage select menu, choose a level and press <A>+<START> to begin that level in the debug mode. =>Debug Mode Controls: When in the debug mode for either Sonic 2 or Sonic 3, the following controls are available: * Press <A> to reverse gravity or <B>+<C> to flip through the character frames. * Pause the game and press <A> to fade out and reset the game, hold <B> to play with slow motion as long as the button is held, or <C> to move forward one frame at a time. * Press <B> to toggle between normal gameplay and the item placement mode. In item placement mode, items can be placed throughout the level with the <C> button. Move forward through the list of items with <A> or backwards with <A>+<C>.