Character mistake: When Guile promises to rescue the hostages while on camera with Bison, he makes it a point to mention Charlie by name to reassure him that he wasn't forgotten. Anyone in charge of a major hostage recovery operation would avoid naming a specific hostage unknown to the enemy due to the special focus that the enemy may put on that hostage for further abuse. This was promptly proven when Bison specifically chose Charlie to transform into a beast due to Guile identifying him as a personal friend.
Character mistake: The Japanese name "Ryu" is pronounced REE-oo. Characters in the film consistently pronounce the name incorrectly as RYE-you.
Answer: In his fight with the guard, Dhalsim gets knocked into some chemicals. This presumably changed him. This is also likely the explanation if he had to do any signature moves from the games, which thankfully, he doesn't.