Unlock Hidden Credits:
When the SEGA logo has fully appeared (after Sonic has run accross it in both directions), tap the letters A, G, E, S in that order. If you have entered the code correctly the hidden credits screen will appear.
Change Tails' name to 'Miles':
When the SEGA logo has fully appeared (after Sonic has run accross it in both directions), tap the letters A, G, E, S in that order. If you have entered the code correctly you will hear a confirmation sound of a ring being collected and Tails' name will read 'Miles'.
ALL Chaos Emeralds:
Enable the 'Level select' code and then play songs 04, 01, 02, and 06 in order at the 'Sound Test' menu.
At the 'Main' menu tap Up, Down, Left, Right on the virtual D-pad. Then tap 'New Game' followed by 'Yes' when the next message appears.
Hidden Options Menu:
Start a new game on 'No Save' mode and tap the letters S-E-G-A in order as soon as the SEGA logo fully appears so you hear a ringing sound to confirm that you have done it correctly. If you then hold down on the screen anywhere with both thumbs and continue to hold through the 'Title' screen you will be taken to the hidden 'Options' menu.
Unlock Hidden Characters:
Complete the following tasks to unlock the corresponidng character.
Collect ALL the Chaos Emeralds.
Beat the game.