Limit application launching to boot disk only

Question

Does anyone know of a way to restrict macOS (High Sierra) to only launch apps stored on the boot drive?

I have several alternate bootable drives on my system (different OS versions, bootable backups etc), but find that in almost every case, when I right click a document, and choose "open with" the system is preferentially launching apps on non-boot volumes, in preference to the ones in /Applications. Eg, right click on an mp4 file, choose Open With the one and only entry for Quicktime Player X, and instead of the version in my dock launching, a new icon appears in the dock for Quicktime, and if I right click and "show in finder", it's on one of my other bootable drives.

I've removed all the external drives from Spotlight, using the Spotlight privacy feature in System Preferences, and tried reloading Launch services (which results in needing to reboot the entire machine to get all my 3rd party share options back), nothing seems to work.

I have to assume macOS is supposed to preferentially open apps from /Applications, and I've got something else wrong, for which this is just a symptom, so if there's some other maintenance thing (eg in OnyX etc) I'm happy to hear about it.

Thanks.

Answer 1

Just for the benefit of anyone else having this issue, and partially to answer @Tetsujin's suggestion - Tinkertool System, a nice GUI app from from Marcel Bresink has a function to both disable automount of specified partitions, and prevent app launching from specified volumes.

Answer 2

I'd suspect you can only do this if each 'other' OS was set to never mount, via fstab - see Time Machine restore to new partition, different computer - & then clear the LaunchServices database [individually for each OS] using Onyx