@PotomacBobI hate to say it, but for outdated system, you'll have to take your system offline anytime you want to use it (I've done this before). But, you save a backup of your executable first, so when you forget (it's inevitable), you can then simply copy it back into the executables library.
Either way, if you ever keep an older executable around, you also keep a copy of your version's installation procedure (your system doesn't need to be online to perform an installation). However, that's a common gotcha, since many are reluctant to upgrade to unproven, untested versions, they instead resort to forced uninstalls to force you to upgrade to the latest crappy upgrade, as they don't make any money if folks don't fork over money for continual upgrades.
(I also have a couple 'lifetime' upgrades, which vanish if I ever upgrade!). And having spent my life doing extensive upgrade testing to uncover bugs, I'll never trust brain-dead AI to exclusively program upgrades (it just don't work)).