I have in fact already tried running it from USB and it seems OK, so it may be that my machine will become a tri-boot or perhaps a W7 / Linux only machine. Besides, over the last month or so I have learned that I can download a frequently updated free O/S called Linux which runs on my machine and is similar to both O/Ss that I am used to running. I mainly use W7 anyway as my work involves me using MS Office at work and my machine is only for work and Internet viewing. For the time being, I will continue using the machine as a dual-boot OS X 10.6 / Windows 7. I think it is extremely unlikely that an Apple store staff member would make that promise or be allowed to back it up if they did make it. I would not object to purchasing it if, and only if, I had a rock solid promise from Apple that if it did not allow me to update to later O/Ss, they would refund the cost of Mountain Lion.
I considered buying that from Apple for the $20 cost, but that, too, is now unavailable to me as it is no longer in the App Store. The reason seems to be that while updates are free, they require that Mountain Lion be installed as a prerequisite.
#Download os x yosemite apple store unavailable install#
Sadly, in fact I cannot use the dmg from the Apple site.Although according to Apple the machine will support some O/Ss later than the factory installed Snow Leopard, attempts to install them fail.