Question: Where does the family live now? Did Winston let them stay in his house forever because he isn't using it?
Answer: The movie doesn't give an answer, since it doesn't really matter in the context of the story. But in all likelihood, the family will continue to reside in the mansion, at least for the time being. Winston loves the Supers, so he'd probably be more than happy to let them stay there.
Question: The theatrical release of this movie had a live-action prologue where Brad Bird, Craig T. Nelson, Holly Hunter, and Samuel L. Jackson thanked us for being patient for 14 years, and telling us to enjoy the movie. Was this clip ever released outside of theaters? If so, where can I find it?
Answer: I've only seen the movie once in theaters, but I've viewed both DVD and Blu Ray openings on YouTube and didn't see it included, but you can find it if you search "the incredibles 2 theater opening." If it has or ever does air on TV, I don't think you'd see it there.
Question: Did they not already know that Jack-Jack had powers after what happened with Syndrome?
Answer: What happened to Syndrome happened high in the air, Elastigirl mentions she can't see whats going on and panics. They never actually see what Jack-Jack is doing and think Syndrome is hurting him.
Answer: The writer and director, Brad Bird, wanted to wait until he came up with a story that he deemed worthy of telling. This wait would ultimately take fourteen years.
Casual Person