Well, first of all, the Super Smash Bros. 2 is Melee, which never featured Sonic or Shadow. Also, Sonic is playable in Super Smash Bros. Brawl, and Shadow is unlocked as an Assist Trophy after unlocking Sonic.
Shadow in not a playable character in Super Smash Bros Brawl; he is only an assist trophy.
no
You can't.
They are not in the game
Unlock sonic in the subspace emissary and you will get shadow the assist trophy.
There is no Shadow in SSBB, but I do believe there are a sticker and trophy of him.
Unlock Sonic
shadow is not a playable character, but you can find him in an assist trophy.
In Super Smash Bros. Brawl you cannot unlock Shadow as a playable character, you can only have him as an assist trophey.
Shadow is not a character in Super Smash Bros Brawl, unfortunately.
You can't get Shadow on Super Smash Bros Brawl, though you can change Sonic's colour to make him look like Shadow.
You cannot become shadow in Super Smash Bros. Brawl.