play 1000 vs matches to unlock character 25, Mr. Game and Watch. There are no characters after that.
25
25
get all the characters
sonic and toad
All of them.
Technically yes sheik is a separate character making 26 characters.
If by "Koopa" you mean Bowser, he is playable from the start. "Purin" or Jigglypuff is one of the easiest characters to unlock
No
No.
No he is not.
You can't get sonic in SSBM only in SSBB and in SSBB you get him at the subspace emissary near the end
You can't. But in Super Smash Bros Brawl you can unlock him by completing Classic mode with ten characters. Then defeat Sonic and you will unlock him and Shadow as an assist trophy.