How to apply Swift Charts, for instance, barmark, without x and y axes and labels?

What's the difference between @State private var and @State var? And when to use the former and when to use the latter?

When user triggers a sheet of a view, it's quite easy to deal with its confirmation action. However, how can I deal with the cancellation action, which means when user taps the cancel button, what they edits can re-become its original version ( I am using SwiftData)?

I have already built an app using SwiftData and now I want to introduce CloudKit features in it, what should I do? I'm totally new to this part. Thank you!