I have Windows 11 on laptop, but Firefox 10 is installed. Is there or do I need to install Firefox 11?

Firefox since 116.0 to current including Fx 150.0.3 Release and Fx 140.10.2esr requires Windows 10, 11 to run. There are no separate versions of desktop Firefox for each Windows 10 and 11. A Firefox 150.0.3 UserAgent or UA on Windows 10 and 11 displays as Mozilla/5.0 (Windows '''NT 10.0'''; Win64; x64; rv:150.0) Gecko/20100101 Firefox/150.0 Windows 11 is basically based on the same NT 10.0 as Windows 10 as to why some sites may think you are using Windows 10. When Microsoft actually makes a new version of Windows hopefully they will do so on a new NT. https://en.wikipedia.org/wiki/Windows_NT#Releases