For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
"The Curious Case of Benjamin Button" does not fit the classic three-act plot analysis, in which a hero commits to and then completes a difficult quest. It is instead the story of an entire lifetime, knitted together with carefully chosen anecdotes and scenes.