Older Mac Systems can get extremely twitter and bisted when they share a drive—even on different partitions, let alone on the same one—unless you are using the likes of System Picker to choose between them. If you do not, you may find that, different partitions or no, Startup Manager is going to be much less befuddled, and less likely to $000F at you, if only the intended System Folder is blest. That means that you will need to remove each unpreferred Finder from its System Folder to root level of the relevant volume, and drop Finder back onto the relevant closed System Folder immediately prior to restarting from that System version. Tedious, but potentially necessary if you do not have System Picker.

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