Differences between the book/movie and this game version
Peeves does not appear in the film, but is battled on a regular basis in this game.
In the book and movie, Neville breaks his wrist after falling off a broomstick from a great height during the flying lesson, what allows Malfoy to steal his remembrall. In this version, Neville is not seen flying or wrist-broked at all, nor he appears at Harry's Flying lesson. Instead, he gets upset after that lesson, when he arrives and suggests Harry that Malfoy has stolen his remembrall.
In addition, Neville's angst was because he lost Trevor again, and upon his remembrall being retrieved, it is implied that Trevor had been left at the Herbology greenhouse causing Neville to panic. This was neither in the books nor the film.
In the book and this version of the game, Malfoy says he might leave Neville's Remembrall on a tree for him to find. In the film, he suggests to leave it on the roof.
In the film and book, Harry's broomstick is jinxed in the first Quidditch match. In this version, neither Quidditch matches have Jinxed brooms or accidents.
In the book, Quirrell summons ropes to tie Harry by snapping his fingers. In the film, Quirrell snaps his fingers to make fire surround the area. In this game, Quirrell does not make fire surround the area, but green ropes do tie themselves around Harry at times.
Norbert seems to appear early in the game, unlike in the book and movie where he appears nearly at the end of the story.
Harry fights Draco with Christmas crackers. Though, in the books and movies, Harry doesn't fight Draco at all until Year 2, despite challenging Harry to a duel (that didn't happen) in the first book.
Harry gets trapped in the dungeons during Potions class, what doesn't happen in the book or the film.