1- Because the child has a paranormal power.
2- Jack became crazy. Because he also worked in that hotel.
3- Jack was who hurt Danny.
4-Because he also worked in that hotel.
5-Stuart Ullman. Because he want Jack kill her family
6-It is a dog costume, not a chipmunk costume, and the character in the book is referred to as the Dogman. In the novel he chases Danny through the hotel, scaring him with absurd sexual threats.
7-The phrase in itself is not scary, the fact that Jack had typed it out thousands of times is. It shows the deteriation of his mental state.
8-Danny's middle name is Anthony and "Tony" is his imaginary friend. At first Danny fears Tony, but he later becomes Danny's source of strength.
9-The idea is that Nicholson's soul has been around for a long time, and that each time he is reborn he returns to the Overlook Hotel and goes on a murder spree. This is facilitated by the evil, restless spirits residing in the hotel.
10-In the book, she is Mrs. Massey, an older woman who is seducing a man much younger than her, until late one night he leaves in the car they arrived in, and doesn't return.
11-Effectively, Danny's shining is what brings the hotel to life. Because he has such an incredibly powerful shine about him, all these weird ghost things in the hotel are able to materialize and reveal themselves.
12-Jack is the same soul as the man in the 1921 ball photo, but that does not necessarily mean he retains their full memory. Jack also has the ability to Shine, but probably does not know how to use, or is even aware that he has the ability to Shine.
