the Apple store changes its code requirements every couple years
true
it will require practically a complete rewrite of the original code
false
In the early years of Swift, the language evolved very quickly, requiring major changes each year.
We may now be seeing a similar evolution with SwiftUI.
Related (non-code) issues also change, like privacy and App Tracking Transparency requirements.
Existing apps will often continue to run, but changes to iOS, and new device sizes, can require an app update.