iTunes 10.1.3.99 is a legacy version that cannot be installed on modern macOS versions (Catalina 10.15 or newer). If you are seeing a message that this version requires macOS 10.13.99 or earlier
Let’s get technical. The fixed version of iTunes 10.1.3 addresses four major issues that plagued the initial 10.1 release:
Apple has aggressively moved away from standalone iTunes installers. Here’s what you face when trying to find version 10.1.3.9: