The problem with downgrading iTunes is that the older version of iTunes on your PC may not be compatible with the newer version of iOS on your device. Also, once you upgrade iTunes, your iTunes Library may no loger be compatible with n older version of iTunes also. So, it is not that simple. Pay particular attention to the fourth paragraph of turingtest2's article above where it says "Windows users who want to use this version need to uninstall the current copy of the iTunes application first. See Empty/corrupt iTunes library after upgrade/crash for steps to revert to a pre-iTunes 12.7 version of your iTunes database, which you may then need to bring up to date to reflect the contents of your media folder."
See the "Make a split library portable" section this article also by turingtest2 if you realty want to be courageous and see how the iTunes Library folder is organized to use the Windows File Explorer to delete old versions of apps:
Make a split library portable