Apple ended support for standalone iTunes on Mac after macOS Catalina (10.15) — iTunes was replaced by the Finder (for device syncing), Apple Music, Apple TV, and Apple Podcasts apps.
I notice you're looking for a specific old version of iTunes (10.13.99) for Mac. itunes 10.13.99 download mac
Apple ended support for standalone iTunes on Mac after macOS Catalina (10.15) — iTunes was replaced by the Finder (for device syncing), Apple Music, Apple TV, and Apple Podcasts apps.
I notice you're looking for a specific old version of iTunes (10.13.99) for Mac.