Clone knuckles:-  play through the game to get super sonic. In super sonics adventure,go to the crashed island. There you see knuckles and eggman. Press a + b + x + y + start after the clip. Then choose knuckles. Go to the same place, and there are two knuckles.

Change view:-  in twinkle park race, press up to toggle between inside, outside, and far out view.

No pause menu:-  press x and y together at the pause menu.

Wallpaper:-  put the disc into your pc cdrom drive. In a directory called extras you will find wallpapers for your pc.

Faster sonic spins:-  continuously tap x or b to spin faster.

Play as super sonic:-  complete the game using all six starting characters to unlock super sonic.
 
Play as robotnic:-  complete the game as super sonic. While the cedits are running press b + a + x + x + y + start.

Be chaos o:- finish the game with super sonic. You must have at least one chao raised and saved to your memory card. Now go to the egg carrier and activate the egg bus (the bus that enables you to renter the level on the egg carrier) and before you're able to enter the level you'll
be stopped by a smoking dr. Eggman in the egg scorpion. He'll shoot down a ray of light and transport you to a fight with "perfect chaos".
Beat "perfect chaos" and you'll have finished the game with "super sonic". Once the credits roll you'll be back at the main screen. Choose the first option and you'll be able to choose "chaos 0".

Be tails:-  controller two may be used for tails after he is obtained during game play.

Faster spins for sonic:-  continuously tap x or b to spin faster.

Select sonic's snowboard:-  just before you enter the snowboarding phase of the ice stage you can press x to obtain sonic's blue snowboard or b to get sonic's yellow snowboard

be reala:-  first of all go to casinopolis on the nights table get to the very top and you can play as nights on 1 level but if you hatch all the
eggberts out of there eggs you can play.

play as super knuckles:-  complete the game using all six characters, then complete it again using knuckles. Now, at the character selection screen, hold x + b.

Play as metallic sonic:-  at the character selection screen, highlight sonic and press a + b + x + y + l + r + left. Press start.

Mega characters:-  unlock super sonic, above, then start another game using that character. Obtain all the crystals and successfully complete the game. At the character selection screen, choose anyone to get a mega version of the character.

Hints:

mystical ruins extra life:-  tail's workshop is located all the way at the top of the mountains in the mystical ruins. Go to the very top and look around to find an extra life. Use the spin attack to zoom over and collect it.

Bonus nights area:-  when playing in the pinball section of the casino level, drop in the top hole to reach another pinball machine. Now drop into the middle hole to reach an area based on nights.

Defeating the whale:-  when on the whale stage(s), run over a speed ramp as soon as it appears. Then, do not press anything on the controller; the cpu will do the rest.

Silver chao egg:-  go to the mystic ruins. Go to the water fall located in the middle of the adventure field. Push the stone that is jutting out of the wall to the right of the water fall. A silver egg will fall from behind the waterfall and float to shore. When it hatches, a silver chao will be born.

Golden chao egg:-  go to the station square area. Then, go to the area when you fought chaos for the first time. Look to the side of the city hall entrance to find egg shaped rock. Take the rock to the building to the left from city hall. Walk to the window to see a golden chao egg. However, if you try to take it the front door will lock. Replace the egg with the rock and the door will unlock, allowing you to leave with the
egg. When the egg hatches you will have a golden chao. 

Black and blue chao egg:-  go to the egg carrier. Then, go the jail area where amy was kept. In the cell next to where she was held is a black and blue egg. Step on the switch to open the door. Take the egg to the garden. When it hatches, it will be a dark grey and dark blue chao.

Take a shower:-  go to the casinopolis zone as sonic and enter the shower area. Get into one of the stalls and push against the wall to give sonic a shower.

Sonic the armadillo:-  go to the past when the master emerald altar is on fire. Move the camera so sonic is facing the screen head on. In the red light, he looks just like mighty the armadillo from knuckles chaotix game on the sega 32x.

Sonic in the sand hill:-  get on top of the ledge and pushing the button to drain the sand. Locate the sand hill cave, but do not enter. Move a short distance back out of the cave entrance. Charge up your speed of light dash, but not to the point where he says "ready". Release, then jump immediately before you go over the little bump or lip. If done correctly, sonic will end up in the sand hill. Note: it is just like the sand hill
in trial mode.

Easy coins with e102 gamma in adventure field:-  go to station square and in the hotel, go up the stairs to the second floor. Stand at the very top step. Shoot your laser at the second button on the floor. Keep shooting to get coins.

Get all five chaos emeralds with the chao:-  to get all five of the chaos emeralds that you can get with the chao, you need to log on to the dreamcast network and go to the chao daycare section. Download one of the chaos that are 999 in all four categories. Return to your chao garden and race him in a chao race. He will leave easily defeat all the other chao. Repeat this on all five races to get the five possible chaos emeralds.

Easy coins with tails:-  find a patch of dark green grass. Move over and stand on it, then twirl your tail around. A group of coins will appear out of nowhere.

Easy coins with knuckles:-  go to almost any spot of dirt or grass, then press a + b to dig down and come up with many coins.

Change station square appearance:-  connect to the dreamcast network through the sonic adventure disc and download the new file.

Special chao:-  collect at least 100 emblems to get access to a special section called the black market on the dreamcast network. A special chao can be downloaded from this area.

Power-up locations:
sonic:
light speed shoes: sewer in station square. Crystal ring: elevator on second floor of hotel. Ancient light: on rock near bridge to angel island.

Tails:-  rhythm badge: follow tikal to past (it is on a pyramid) jet anklet:in the sewer behind twinkle park.

Knuckles:-  fighting glove: in the cave near angel island. Shovel claw: on a cliff behind big the cat's house.

Amy:-  warrior feather: defeat hedgehog hammer for the first time. Long hammer: defeat first place score again.

Big the cat:-  life belt: in the lake in the cave leading to angel island.
Power rod: in forest under big's bed.
Lure 1: in sewer behind twinkle park.
Lure 2: in a cave in the forest.
Lure 3: in the icecap level.
Lure 4: in a prison cell on the egg carrier.

E-102 gamma:-  jet booster: in the ammunition room of the egg carrier. Gun upgrade: in the room opposite the ammunition room.

Getting every emblem:-  sonic: 30 emblems to collect in sonic's action stages.
Tails: 15 emblems to collect in tail's action stages.
Knuckles: 15 emblems to collect in knuckles action stages.
Amy: 9 emblems to collect in amy's action stages.
Big the cat: 12 emblems to collect in big's action stages.
E-102 gamma: 15 emblems to collect in e-102's action stages.
Adventure field: 12 emblems to find in adventure field.
Mini games: 10 emblems to collect in mini games.
Chao races: 5 emblems to collect in chao races.
Complete the game with all six characters to get 6 emblems.
This brings the total number of emblems that are collectible in the game to 130.

Chao moods:

heart: happy
swirl: angry
question mark: confused
exclamation mark: surprised
xx over eyes: angry
--over eyes: happy
half closed eyes: tired
waving arms: wants attention
flailing arms: angry