I was very irritated with the backward buttons problem with the FC 3 so I decided to see what I could do about it.
Unfortunately there is no easy fix for the SNES problem but you can fix the problem with the Regular NES games Very simply and It won't affect the other systems buttons.
Simply open your controller and look at the circuit board. you should see a row of 6 diodes on it. Look for the second diode from the right. (I have circled it in yellow).
like this:
http://www.digitpress.com/forum/atta...1&d=1231789464
Simply remove this diode.
It should look like this after your done:
http://www.digitpress.com/forum/atta...1&d=1231789464
At this point the 'C' Button becomes another 'A' Button. so you have the ability to play using the 'A' Or 'C' Buttons as a NES 'A' button. Of course the 'B' Button remains the same. This change will not affect how other systems play on the FC3. (Genesis or SNES) It only affects NES games.