I wanted to clarify some things about how the App Store worked in the past. In a previous thread of mine, I was told that in the past your OS was linked to your Apple ID. (Starting with Sierra, that is no longer true.) I'm not sure that I understand what that means. For instance, I have an old MBP that came with Mountain Lion. Because it was after Snow Leopard, it didn't come with a "recovery DVD", but because this was several years ago, old versions of OS-X were still available online. (I believe.) So with that MBP, how would I have gotten ahold of Mountain Lion? Would I have had to buy Mountain Lion to see it in the App Store? Would I have needed to have an Apple ID to see it in the App Store? Or would I have needed both an Apple ID, and to have bought Mountain Lion, to see it in the App Store?