I have Photoshop Elements 12. My laptop crashed and I have to reinstall the program. I have the CD and can install it from there. Can I then update to Elements 2020 and restore my catalogue from my backup?
You may be able to update your catalog to version 2020, but you are jumping five versions of the software. So I'd recommend downloading the free trial of the software and seeing if it works before I paid for the purchase.
Meantime, there is no reason to re-install version 12 in order to install the upgrade. The upgrade is a full version of the program and it does not require the presence of an older version of the program to install. The "upgrade" is actually just a special price for current owners of the program.