Your best advice for codes on this game would be
http://www.gamefaqs.com
However, if it's anything like the first Street Fighter Collection, Super Street Fighter 2 Turbo only has the normal (non-super carrying) Akuma.
Although I
do remember a code stating that if you beat the game with both the turbo and normal version of the fighters, you could open up a dipswitch mode to play with-and a switch where you could enable Shin-Akuma.
I can't confirm it or not. I can't bring myself to play SSF2T in marathon sessions like I used to. Especially with KOF'98 on DC.
But I do still play it occasionally. Shin-Akuma really isn't the meat and potatoes of the game. The novelty will wear off soon. You may be well suited to Zangief's ending though. The McHale Gorbechov appearance is priceless. And in the traditional Soviet tradition, Everybody dance!
Hope you have fun with it though. Let us know how chopped up a game Capcom's rehased. (Or how well they've smoothed it out, either way.)
Edit: Traditional Traditions? How, wordy....and traditional.