In "Star Wars: Episode III – Revenge of the Sith," the confrontation between Anakin Skywalker (who becomes Darth Vader) and Obi-Wan Kenobi is a pivotal moment in the story. However, it seems you might be conflating different elements or scenes, as there isn't a specific instance where Vader asks Obi-Wan four questions or discusses five things in the films.
If you're referring to their encounter on Mustafar, Anakin confronts Obi-Wan as tensions rise, and their dialogue serves to highlight the emotional stakes of their relationship, Obi-Wan's attempt to reason with Anakin, and Anakin's descent into darkness. This intense dialogue sets the stage for their tragic duel, showcasing Anakin's conflicted feelings about power and loyalty while maintaining a sense of the deep bond they once shared.
If you have a specific scene or dialogue in mind, please clarify, and I’d be happy to explore it further!