You cannot unlock Oni.
Either 'cause you didn't unlock her or you got the ORIGINAL Street Fighter 4. Other than that, she should be there.
read the complete details here - http://j.gs/1010114/sf4-unlock-characters
There is no way to unlock the arcade version of Akuma.
read the complete details here - http://j.gs/1010114/sf4-unlock-characters
Super Street Fighter 4 is basically the same game as Street Fighter 4. SSF4 features everything SF4 had, with more modes, moves, and characters. Super Street 4 will tweak some minor things, but by no means is this a different game than Street Fighter 4.
you need to compleate Charpter 4 mission 2 to unlock him, and the password to skip there is: 1hr9
Super street fighter 4 comes out on April 27th
Street Fighter
street fighter (war) and the band is sick puppies
Evil Ryu appears in Super Street Fighter 4: Arcade Edition.
No, but if you are into street fighter, I heard street fighter 4 is coming out for the DS.