Is it possible to download and install multiple versions of Safari on macOS? I need to test something out on my MacBook with the latest version of Safari (13), but I don't want to update my current Safari browser to the latest version. I want to be able to keep my current older version of Safari UNTOUCHED and the newest version of Safari both installed and usable on my Mac computer. Is this possible?
Updates to Safari tend to include updates to the WebKit system framework on which Safari relies. (The WebKit framework is separate from the app, and is then available to other apps.)
Executing an app that was built for a different framework from the last one you installed is likely to cause problems.
No, it is probably not possible because Safari is a part of macOS. New versions of Safari come with macOS but you can try finding the Safari downloads at https://support.apple.com/downloads. Double click the .dmg file and complete the installation.