Cody Fairless-Lee

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.

Brian Katcher

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.