What is the safest way to recover when an Ionic CLI upgrade fails midway and leaves mixed versions?

I am planning a global upgrade of the Ionic CLI via npm and want a clear recovery plan in case the upgrade fails partway through. My understanding is that the npm install -g @ionic/cli process is not atomic, so an interrupted install could leave a mixture of old and new CLI files in the global node_modules directory, with no built-in rollback command.

The constraints I am working under: the project pins specific Cordova/Capacitor plugin versions that may be sensitive to CLI version changes, the machine is macOS so global npm permissions matter (I want to avoid sudo if possible), and I need to confirm afterward that exactly one CLI version is installed and that it is compatible with the project's Ionic Framework version.

My specific questions:

1. After a failed upgrade, is reinstalling the previous known-good version with npm install -g @ionic/cli@<version> sufficient, or should the npm and Ionic caches be cleared first to avoid reinstalling corrupted artifacts?
2. What is the most reliable verification that recovery succeeded — is ionic info plus npm list -g @ionic/cli enough, or should a test build be run before trusting the CLI again?
3. Is there any supported way to make CLI upgrades transactional or at least detect a partial install automatically?