To permanently 'install' or more accurately flash anything to the Switch, it needs to be signed with Nintendo's personal key which is not kept on the console but rather somewhere in their HQ. Even on the 3DS, we could never permanently flash any CFW because these consoles are designed to reject anything not properly signed. B9S is not a CFW, its an exploit much like Fusee Gelee (but with more steps) that allows a CFW like Luma to be loaded automatically but not permanently.
Not the entire exploit chain. Parts of it were patched out, but it hasn't been fully patched out hence why it is being kept under wraps.