If you have a valid Creative Cloud subscription (individual, team, or school license), Adobe actually allows you to download and install old versions. You just need to know where to look.
If you commit to an Adobe Premiere Pro old version, you must accept the trade-offs. adobe premiere pro old version
—projects saved in newer versions cannot be opened in older ones. To address this, you can develop a "Version Downgrader" feature as a custom UXP plugin If you have a valid Creative Cloud subscription
There are several strategic reasons to stick with an older build rather than upgrading immediately: or school license)