Build 15035 was released to Windows Insiders on the Fast Ring (and later Slow Ring) in February 2017. It belongs to the Redstone 2 (RS2) development cycle, which eventually culminated in the public release of the Windows 10 Creators Update (Version 1703).
To understand the value of build 15035, we must rewind to February 2017. At this time, Microsoft was deep in development of the Creators Update (version 1703) , which would eventually release as RTM build 15063. windows 10 build 15035 media builder link
Build 15035 is a prerelease branch build (fbl_impressive). It sits chronologically between the Anniversary Update (14393) and the final Creators Update. What makes 15035 special is not its features—which are largely identical to the Creators Update—but its driver signing and hardware compatibility. Build 15035 was released to Windows Insiders on
If you are not an advanced user testing legacy software, it is highly recommended not to use Build 15035. It is an unstable, pre-release build that has long since been superseded. Summary: The official "Windows 10 Insider Preview ISO"
If you are looking for the version of Windows 10 that replaced 15035, you want the Windows 10 Creators Update (Version 1703). You can find the official media creation tool for that era on the Microsoft Software Download site, though it will default to the latest version (22H2) unless you use third-party scripts to fetch older release ISOs.
Summary:
The official "Windows 10 Insider Preview ISO" page on Microsoft's website typically only retains downloads for the most recent Insider builds and the latest stable versions. Build 15035 has been removed from the public server rotation.