Can I download and run a 12.4 Xcode version if I have been installed already with an Xcode 13 version.
if yes, what's the safest way to do so?
Can I download and run a 12.4 Xcode version if I have been installed already with an Xcode 13 version.
Yes, you can. Just download and unpack into different folder (or with different name). Every Xcode Version is standalone and contains everything needed within own bundle.
Renaming is optional - only if you want to place it aside with other Xcode version into same folder. Just download, unpack, and run - that's it.