Hi William,
I’ll clarify what each of these accomplish.
Update & Close doesn’t save your pages back in the app, it simply has it stored in your browser. If you navigate to another page all changes will be lost. Update and Save on the other hand is a ‘hard’ save and will apply all your changes to your app.
The version comment enables you to make a note which is espcially useful when working with multiple users. You can indeed see these changes as well as roll it back to any version you wish.
You can see all your page versions by clicking on the little arrow next to the page name:
You can also see summary of all changes inside your settings:
These are new features, you can see this post for more details: Versioning, Backups and Restores