Question: After young Willy sees his childhood home disappear, where did he live and grow up?
Question: Are Violet and Mike stuck as being blue and stretched out permanently?
Answer: It's left vague in the film, but in the book, it's made clear that yes, they are stuck that way.
Answer: In the original movie with Gene Wilder, Wonka assures Charlie that "they will be returned to their nasty selves." In this version they are stuck like that forever as a lesson to other children.
Answer: It's unknown if they'll stay that way for the rest of their lives or if they'll eventually return to normal.
Question: Does Violet stay blue and Mike remain incredibly thin and tall after they leave the factory?
Answer: There is a scene at the end of the film showing the children leaving the factory. It shows the changes ARE permanent. Mike stays stretched and Violet stays blue. She is also impossibly flexible: https://www.youtube.com/watch?v=jBOvtKI73yc.
Answer: In the book, it's implied that they did.
Answer: We are never shown what happened to him but he may have gone to live with relatives or he was simply put into an orphanage.