Sonic The Hedgehog

Enable the "Level select" code. Select the "Bonus level" option on the level selection screen. Obtain the Chaos Emerald, reset the game, and repeat the process until all of them are in your possession. Allow the game to continue after obtaining the last Chaos Emerald to start in the Green Hill Zone.

Note: When you collect all of the Emeralds, you will not become Super Sonic, but you will be practically invincible. Try the following. When you have no rings, get attacked by something. Sonic will fall back (as if he had a shield on him), but he will not die. However, Sonic will die if he falls off of the edge of something, sinks underwater, etc.

Complete Green Hill Zone 1-1 or 1-2 in 29 seconds or less to receive 50,000 bonus points.

At title screen type in :up,A,,down, A,left, A ,right ,A then A,start. This is a special level select,, it also allows you to hear the sounds and music.

At title screen type in :up,A,,down, A,left, A ,right ,A then A,start. This is a special level select,, it also allows you to hear the sounds and music.

For extra points, pass any zone in a certain amount of time. For the best bonus, enter the Debug
Mode code. The clock will freeze and you'll always score a 50,000 bonus!

There is a code called control mode, which is required before activating this code.

To activate control mode, press UP, C, DOWN, C, LEFT, C, RIGHT, C at the title screen, but before pressing start to begin the game, press and hold A as you hit start. Now, rather than just being in control mode, you can enable config mode by pressing button B.

Sonic will morph into a ring, and the arrows can move him anywhere, even in the air, or through obstacles such as walls, floors, or even ceilings {GREAT FOR TELEPORTING!}.

You can change the item Sonic appears as by hitting A while in config mode. Button B makes Sonic normal again, and button C will place the sprite that you have selected for Sonic to appear as. For example, you press B, and Sonic becomes a ring, press C to make a ring appear exactly where the ring icon is.

WARNING!: This will distort several different things, such as the score, time, and other various icons throughout the game such as the finish sign at the end of the first two acts of each zone that spins when Sonic shoots past them, and the small score icons that appear whenever Sonic jumps high enough after finishing a level. That is all I have noticed in my time playing the game, but there could be more out there yet. The game is still quite playable this way, so it should not hurt you.

Note: This code is for the Japanese version.
At the title screen, press Up, C, Down, C, Down, C, Down, C, Left, C, Right. You'll hear a ring sound. Start the game when holding A to be in Config mode that the Score and Time are distorted. Press B to enable Config mode, that Sonic morphs into a ring. Press A to switch through different items, Press C to place the sprite, hold A and press C to go backwards on selecting items, move around with the D-Pad, or Press B to morph back to Sonic.

While the demo is playing, hold A + B + C. Sonic will get confused, lose his place, and possibly die.

Enable the "Debug mode" code. Press B when Sonic is running with the animals at the end, then turn back into Sonic. You can nowcontrol yourself.

At the title screen press up c down c left c right.start the game.then,when you press pause then a,the game will restart.press c the game will move one frame,press b,the game will be in slow motion!

Hold A + B + C during demonstration mode for force Sonic to run into objects and act strangely. Note: This may also be done during the ending sequence after completing the Final Zone.

Enable Control Mode. After pressing Start to begin a game, hold A until you see Sonic. If you
see a bunch of hex numbers on the top of the screen, you're in Debug Mode.

To start debugging, press B, then you can select any sprite in that level and put it on the screen.
To select a different sprite, press A, and to place it on the screen, press C. Note that sprite
selection is different from Zone to Zone. Also, instead of displaying the time elapsed, it displays
the number of sprites currently on the screen. Control Mode functions work as well.

Note: This only works on the first production releases of Sonic.

Press Up, C, Down, C, Left, C, Right, C, Start, then hold A at the title screen. Continue to hold A until game play begins. Screen coordinates will appear instead of a score and the number of objects displayed will appear instead of the time remaining. Use one of the following controller actions to enable the corresponding debug code. Note: This code may only be enabled on the first version of the game.

Object transformation
Press B during game play to change Sonic into a game object. Press A to change into a new object. Press C to place an object on the screen. Press B again to revert back to Sonic. Note: The type of object that may be selectable will vary from level to level.

Invincibility
Sonic is, by default, invincible in debug mode. Note: Sonic can still drown, be crushed, fall and die, etc. He is only invincible to enemy attacks.

Slow motion
Pause game play and hold B.

Restart
Pause game play and press A.

Frame advance
Pause game play and press C.

In the Japanese version, press press Up, C, Down, C, Down, C, Down, C, Left, C, Right at the title screen. A sound will confirm correct code entry. Pause game play, then press the buttons described above to activate slow motion, restart, and frame advance.

During the demo, hold C. Sonic will crash into walls and get hit by enemies.

In Green Hill Zone - Act 3, there is a 1-Up at the very bottom of the level. Collect it along with
enough rings to make 100 for a second life. Next, grab the 1-Up at the top of the loop-de-loop
and die. Repeat until you have enough lives.

This cheat allows you to start at the First Level with all the Emeralds, and with lots of Continues.
Use the Level Select cheat (see above) to get to the Special Zone. When you get the Emerald,
and have entered into the First Zone, press Reset.

Use the Level Select cheat to get to the Special Zone again. When you get the next Emerald, and
have entered the First Zone, press Reset again.

When you have all the Emeralds, continue on with the first level. You get to keep the Emeralds
and the Continues accumulated so far.

Enable the "Debug mode" option. Collect fifty or more rings (or just transform in a ring and get fifty or more). Go to the end of the level and do not pass the ending sign. Press B button and look through your transformations. You should find the Big Ring (at the end with fifty or more rings) in your options for transformations. You can now place another Big Ring. If you place a Big Ring before you pass the sign and behind the sign then go inside the ring the game will glitch. You cannot move (including using Debug mode), see yourself, or hear yourself. Note: This was done in Green Hill Act 1;

Enable "Level select" and "Debug mode" codes. Put a lamppost just before the sign at the end of the level. Press B to transform back into Sonic and hit the lamppost. Get out until the lives read "1" at the bottom of the screen. Spin the sign to end the level. Wait until Sonic walks out of the screen. Enter debug mode and go under the sign to get out again. The "Game Over" message will appear while the credits are being shown. You now have unlimited lives.

Enable the "Debug mode" code. Go to Green Hill Act 2 and find the location with a spinning wheel, two or three falling blocks, and a floor of spikes. If needed, use "Debug mode" to find this area. Make all the blocks fall and land on the spikes, but away from the land at the end of the blocks. You should lose all of your coins and bounce forever until you reset. Debug mode is needed for default invincibility. For an alternate method, get all the Chaos Emeralds for invincibility for spikes enemies, etc.

Enable the "Debug mode" and "Level select" codes. Select Special Stage at the level selection screen in Debug mode. Turn into an object and exit the compressed area (The place that Sonic is always in without Debug mode). When you think it is far enough, turn back into Sonic. You may seem to fall for awhile, but if you wait long enough you will find a "W" (possibly for the renamed Clock Work Zone, that was later renamed Scrap Brain Zone. They renamed the zone because they forgot the "W" in the games coding) labels that say 1 Zone; 2 Zone; and 3 Zone. There is also the Sonic !-Up as seen in the manual, but never seen in the Special Stage.

Enable the "Level select" and "Debug mode" codes. Enter the Special Stage. Transform into an object and go outside the Special Stage maze. Fall into the place with all the discarded objects and look for a red Chaos Emerald. If you find the correct one (there are multiple ones, but only one is collectable), the music will pause for a moment, then the emerald chime will play and you will spin out of the Special Stage as usual. When the results screen appears, you will see that you have six red Chaos Emeralds and it will say "Sonic Got Them All".

Enable the "Debug mode" code. Go to the end of Star Light Zone Act 1 without passing the sign. Press B and go under the floor at the end to find a secret underground hideout.

Hit him before he gets out his wrecking ball. While he swings the ball, jump (but do not hold it down) and hit him. Keep doing this until he is defeated.

Enable the "Debug mode" code. At the beginning of the level, create 50 rings and have Sonic collect them. Then, take Sonic to the end of the stage where you the giant ring. In the special stage, turn Sonic into an item and bring him to the end of the stage where the emerald is located. Turn him back and he will immediately get the Emerald. Repeat this until you have all six.

Enable the "Debug mode" code. While in Special Zone, transform into something then go as far left and down as possible until Sonic stops shaking. Turn back into Sonic. You will fall to a place which is spinning. Look around to find every different Emerald. Note: If you fall off this place, you will fall back to your original location. To prevent this, transform and repeat the process. This works in every Special Zone.