Version History In Photoshop | How To | Restore Previous Files | Undo | Graphicxtras
You can find the version history panel in the Photoshop window menu as well as in the file menu (confusingly). The panel shows the date and time of a saved entry. This only works if the file is save to the cloud, it is not for your own machine. You can run through all the changes and when you click and entry, the file will be displayed in the preview
To activate a file from the panel
Go to the entry and on the right side there are some dots, click that menu and you can name this 'file' and you can revert to this and you can also open it in a new tab, effectively creating a new file to work with.
What do you get
You get all your layers back but the history of the work is not returned etc but you can now select the layers and tweak them
How to save the work to the panel
Go to the save command and save it and it will be stored as a version. You can also close it and it will also be saved which is slightly confusing.
It should be noted that the history / undo will be lost after 30 days, they are deleted. You can mark them and they will then be a marked entry and will not be automatically deleted.
The ultimate undo
This means none of your work will be lost, you can undo all the way back to your earlier entries. Of course, it does depend on you saving the work as you go