Any input lag?
None as far as I could tell. It was smooth sailing and rather easy to play.
Sound issues?
Wonder Con is pretty loud, so all I could hear coming from a DS is the louder noises like Ciel's screams or Zero's Z-Saber charge attack.
How did they fit it to the screen?
Wide screen. It seemed like it fit perfectly the screen. They didn't leave it squared, leaving two black lines on the sides like the GBA version on the DS. They didn't streched it either to "make it fit". This I remember clearly since what excited me the most was your clear and sharp it was on the DS.
Can you assign multiple actions to one button?
I am pretty sure. I just quickly skimmed the Start Menu to change a few buttons so I can start playing.
Multiple Buttons to one action?
Not sure. Same reply as above.
Dedicated P. and S. Weapon buttons?
No. You can change them to your liking.
Command Dash option?
Pretty sure. Same reply as the Multiple Buttons one.
How cool is the game select screen?
God help me if I remember. It was cool. New art I haven't seen if I remember right.
Did they change any of the dialogue?
In the 20 mins that I played, the dialogue seem like it is the same. However, I don't remember all of the dialogue from the GBA version, so I can't say for certain.