Boarding pass checks etc are independent of the security checks. At least security never checked my boarding pass or ID, it was usually a step before and after security checks.

I don’t think so- I believe it just checks the outstanding warrant/no fly list and that’s all, but I could be wrong.

No, it checks that you have a boarding pass: https://www.tsa.gov/travel/security-screening/credential-aut...

> CAT is linked electronically to the Secure Flight database, which confirms travelers’ flight details, ensuring they are ticketed for travel that day.