Hello,
To update the WoodMart Theme and WoodMart Core plugin on your Site, you can follow-up the Theme Documentation guidelines here: https://xtemos.com/docs-topic/update-the-theme/
Also, please take complete Backup of your Site first before updating.
Further, regarding the previous version of the Theme. You can download your current Theme version before updating so that you can have the previous version of the Theme available.
Whereas, simply if you have the Backup of the Theme first before updating then you won’t need anything else. If any mishap happens after the Update on your Site and you want to revert back to the previous version you can run the Backup of your previous version on your Site that you just downloaded.
Hope we have cleared your doubts now !
Best Regards.