Assuming you can upgrade to the latest non-Creative Studio versions (version 14.5) on an Intel Mac, no user-created files should get corrupted. User files are not updated. Some people seem to have problems locating files stored in iCloud after some updates but I'm not sure any have actually lost any. They often don't report back to let us know.
Before updating, you can copy the application files to somewhere else on your drive then rename them and you'll continue to have the old versions after the update. I put the version number at the end of the name. I wish I'd thought to do this a long time ago. The oldest one I have is 13.1. However, if you open (and save or autosave) a Numbers file in a newer version you won't be able to later open it in a previous version. Numbers usually "upgrades" the documents when they are opened and the older version will no longer open them.
I'd avoid the Creative Studio version of Numbers et. al. for now. If you get a pop up that there is a new version of Numbers available, don't do it. Even though the iWork apps are still free to use (for now anyway), they include some pay-to-play stuff and people are complaining about it being intermixed with the free stuff and they keep getting popup ads to buy Creative Studio. Very much a turn off. If Apple ever decides to make the iWork apps not free, I am out of here (after 18+ years).