SUPPOSEDLY the spirit of the hotel (or previous caretaker) takes over Jack and he's no longer Jack; he's the former caretaker. The picture at the end, which also confounds me, may be meant to prove conclusively that Jack had been completely "inhabited" by the spirit. I think the other 2 things you mention are flashbacks to past events in the hotel to show that Jack is experiencing bits of the past as he's gradually taken over by the spirit. The real deal is that Stephen King's stories have events that don't have any explanations. What I mean is, he doesn't create a fictional reality that gives an explanation for why something fantastical happens. That's why I quit reading him. You want some kind of satisfaction at the end of a novel that you understand the reason all those things happened. It's not enough just to read about them happening. It's cheating the reader, in my opinion. It makes me furious. Director Stanley Kubrick was famous for enigmatic content in some of his movies (e.g., "2001"), so I guess he had something in mind when he inserted the photo. But he's dead now, so unless he told someone we'll never know.