The exposition of the book is when Harry Potter begins to get his acceptance letters from Hogwarts. We see Harry and his family here.
letter
letter
letter
letter
The inciting Incident of the story is when Harry and his family are on some get-away and go to this big building in the middle of the ocean, and Hagrid comes to pick Harry up himself after his parents refuse to send him to Hogwarts, where he meets his new best-friends.
Harry, Hermione and Ron find and go through the mystery trap door ro try and fight off whoever was messing with the stone, that was originally guarded by a 3-headed dog.
The climax of the story was when Harry uncovered and confronted Professor Quirrell, who is under the Imperius Curse. Harry’s battle with Professor Quirrell was the most intense part of the story, which makes it the Climax.
being controlled by Voldemort
Harry prevents Voldemort from using the Imperius Curse to control Professor Quirrell by burning Professor Quirrell, revealing he was a Horcrux.