I had to roll back my OS X version, and ended up with High Sierra (factory install, then some security updates). But when I imported my settings from Time Machine, I managed to end up with numerous programs that require a later OS X version, and will not open. These include Notes, ctivity Monitor, Terminal, and various dyn libraries needed by other programs. How can I bring apps and libraries back to the OS version I have (i.e., High Sierra)? I do not have a usable backup of the apps folder for this version. Is there an alternative to doing another full instal of High Sierra?
I plan to upgrade to Catalina next, but the catalina installer is among the apps that run but fail, with a complaint about incomptible versions.