Street Fighter Alpha The Movie

Now I have watched this film numerous times and im wondering the following:

What was that Move he did against the doc at the very end of the movie? it had a blue aura unlike the red aura of the Dark Hadoe and and Ryu didnt look evil or anything, IMO I think it was the Light Hadoe (dunno if such a move exists or not but meh).

Secondly Akuma has allegedly mastered the fighting style used by Ryu by useing the Dark Hadoe and Ryu's master Goken said that they must never allow the Dark Hadoe into their fists but if it is part of their fighting style why on earth shouldnt they use it? Obviously they shouldnt use it cause they arent evil but the fighting style itself was supposed to be used to kill their opponents (ie should be used by evil people) so why on earth did Goken train under such a fighting style? why didnt they just study another style? its a bit weird if you ask me.

Thirdly Shun... why dont we ever see him in any of the games (unless he is and im obviously missing somthing.