There are so many cases of the copyright office rejecting the request to register copyright for AI-generated works. Here’s just one example: https://www.copyright.gov/rulings-filings/review-board/docs/... (skip to section III).

Yes[1]. Copyright applies to human creations, not machine generated output.

It's possible to use AI output in human created content, and it can be copyrightable, and substantiative, transformative human-creative alteration of AI output is also copyrightable.

100% machine generated code is not copyrightable.

[1] https://newsroom.loc.gov/news/copyright-office-releases-part...