One of my co-authors, meaning well, edited last year's form with this year's information rather than duplicating it first. I'd like to restore last year's form only for archival purposes, but being able to restore a prevous version would also be useful when I change my mind and want to go back to an earlier design.
While you are in editting the form and are in the same session you can undo/redo changes but as soon as you close the browser or go back to the dashboard (My Forms) by closing the form there is no way to get back to an older version of the form. You would have to do the reverse changes manually.
In the future you should do a duplicate (like you mentioned) or save (export) the design file so that you can re-import it to create new versions without affecting the original.
Thanks so much for the answer! Will be sure to share that with my co-authors....