I have a downtime thing and I know the passcode but when I approve it for any amount of time it doesn’t work also my settings app crashes when I open screen time
iOS 18 glitch
Do you mean Screen Time? There seems to be an issue with the Screen Time settings in the iOS 18 betas.
You should raise a Feedback report: https://www.apple.com/feedback/ then post the FB number here. Others have already raised such reports, but if Apple receive a lot of them they'll fix it.
Screen Time is a main feature of iOS so I would say this would get fixed anyway, but your report might be the one that includes the relevant information allowing them to fix it.