You've hit a pet peeve of mine: old libraries cannot just be copied from old CD/DVD's, but instead you have to completely install the old version, grab the library, and then uninstall the un-needed version.
You won't cause any harm/problems by installing as many old versions as you want. Launch the old version with just the default template and do a Check for Updates so that you download the most recent fixes to the library. Copy the library some place safe, and then uninstall the AC program you just installed.
The main issue you'll run into is that typically the LAST installed version of AC is the default version your system will look for if you double-click a PLN file to open it. (Many of us recommend never opening files that way anyway... just because you never know what version the file SHOULD be opened with. The File Open dialog, on the other hand, displays the file version in the lower right corner.) You can fix that in Windows or Mac with steps in another thread... If you're not sure how, one of us can post.
It is also possible (likely) that installing an old version will over-write the current WIBU/CM driver with an old one ... and so you may have to download and install the 16 driver again (from graphisoft.com).
Finally, it is possible that the Windows Explorer / Mac Finder plug-in that displays the preview icons of MOD, GSM, etc files will be the old version. Not sure how to get that updated other than to reinstall 16...?
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB