Windows 11.3 is an OS Concept created by 7Zeb, the YouTube video for this was uploaded on December 23, 2024. The RTM build is unknown.
Development of this operating system concept appears to have been started 1 day after BlueOS 1.0 was finished (October 2, 2024), with build starting to come out.
Windows 11.3 Build 1
Windows 11.3 Build 2
Windows 11.3 Build 3
Windows 11.3 Build 4
Windows 11.3 Build 5