I created the wknd site. I edited a page, and changed the layout, expecting to be able to ctrl-z to undo it. No undo. So next I look for a "cancel" button, but cant see it. I cant see any way to revert changes.
AEM does not come with any OOTB functionality where it will create version for each edit when user performs any action. It creates only version when a page is replicated/activated. Once you replicate the page it will add a version stamp and will allow the user to revert it back to the previous version only if it's available from the timeline rail. Please see the screenshot below:
Also Please refer the below documents from Adobe regarding page versioning: