These days…
You can't roll back iOS.
You can't roll back iOS apps.
You can't roll back MacOS?
You can't roll back MacOS App Store Apps.
You can't update iOS or MacOS to its last point update if a newer release exists; they insist on making you take a fully up-to-date leap. (I think MacOS might be a bit more flexible than iOS on that front and security fixes might be allowed and obviously, you can get to the last point update if you do updates in a timely fashion).
(Maybe you can roll back MacOS on Apple silicon, I’m not sure. Apple silicon Macs are more locked-down security-wise. I don't think you can roll back to an earlier MacOS release via Snapshots either).