I have many cds w/ keys from many years of Adobe Photoshop. My late brother in law was a professional photographer. CDs w/ Keys I have are:
Photo Shop CS, Photo Shop CS2, CS5, CS5.5, CS6 & CS7. The later versions labeled Upgrades.
I am trying to determine which I can use. None of the previous installs are active anymore. The PCs were wiped and disposed of. Can I use any of this and if so, do I have to start w/ the oldest and upgrade or can I jump to near the end?