was released to allow developers to target new APIs specific to this version. Windows Blog Key User Features and Refinements

To understand the hype, one must first decode the versioning. Microsoft’s versioning strategy for Windows 10 ties build numbers directly to the development cycle of the "feature updates."

If you were a Windows Insider in 2019, check your Downloads folder in the Microsoft Insider portal. While most links are dead, Microsoft occasionally keeps older RTM candidates available for enterprise partners via the Windows SDK and Emulator archive (though the full OS ISO is rare).