I have a macbook that is running OS X 10.8 (Mountain Lion); for various compatibility-related reasons I would like to upgrade the system, but not to El Capitan. Yosemite (OS X 10.10) would be dandy. The App Store, of course, only offers an upgrade to El Capitan, currently the newest OS X version.
I know that it is possible to restore a computer to the OS it had prior to an upgrade, but is it possible to upgrade to a (never-seen before) OS version that is not the latest available?
Edit: This question is related (but only if Yosemite had been downloaded via the App Store in the past).