You can in the multiplayer mode, but not in the main story.
The only way you can get a Tails Chao and an Amy Chao in SA2B without Action Replay is by via hacking.
I think you can play as Amy in story mode but you need to use Action Replay. You can play as Amy in 2 player mode, she is already unlocked. To unlock Amy in kart mode you have to successfully complete all of Sonic's stages and missions with the ranking "A". I hope that helps.
Shadow, Eggman as a playable character, Rouge the bat, Gerald Robotnik, The President and his assistant.
When you turn on the DS, the main screen is the menu.
menu
After your chao has reincarnated twice or more, give it EVERY ANIMAL IN THE GAME and NO CHAOS DRIVES. All of the animals are:PenguinOtterSealPeacockCondor (SA2B only)ParrotSwallow (SADX only)Boar (SA2B only)Rabbit Deer (SADX only)Kangaroo (SADX only)Cheetah (SA2B only)Tiger (SA2B only)GorillaElephant (SADX only)Lion (SADX only)Bear (SA2B only)SkunkMole (SADX only)Koala (SADX only)Ram (SA2B only)Raccoon (SA2B only)Unicorn (SA2B only)Dragon (SA2B only)Pheonix (SA2B only)Bat (SA2B only)Sea Monster (SA2B only)Skeleton Dog (SA2B only)Give it the animals of the game it's onMake sure you raise it to be neutralI recommend making a check-list so that you ensure that it works. If you have any difficulties in making a chaos chao, feel free to message me as I have some chaos chao (eight to be exact) so I should be able to help. - Raiwolf
You can press the escape button to go to the menu screen
there isn't a sa2b for PC unless u download a gamecube emulator and the ROM
sorry, what I meant was you hold the left mouse button on the start menu and drag it to the bottom of the screen
After your chao has reincarnated twice or more, give it EVERY ANIMAL IN THE GAME and NO CHAOS DRIVES. All of the animals are:PenguinOtterSealPeacockCondor (SA2B only)Parrot Swallow (SADX only)Boar (SA2B only)Rabbit Deer (SADX only)Kangaroo (SADX only)Cheetah (SA2B only)Tiger (SA2B only)GorillaElephant (SADX only)Lion (SADX only)Bear (SA2B only)SkunkMole (SADX only)Koala (SADX only)Ram (SA2B only)Raccoon (SA2B only)Unicorn (SA2B only)Dragon (SA2B only)Pheonix (SA2B only)Bat (SA2B only)Sea Monster (SA2B only)Skeleton Dog (SA2B only)Give it the animals of the game it's onRaise it this way with dark characters (Shadow, Rouge, Eggman) if you're on SA2BRaise it this way whilst only feeding it dark fruit if you're on SADXI recommend making a check-list so that you ensure that it works. If you have any difficulties in making a chaos chao, feel free to message me as I have some chaos chao (eight to be exact) so I should be able to help. - Raiwolf
the cheat screen is the career menu.