I recently had to load RSLogix5000 rev 20 to use with an existing PLC.
I purchased a Studio 5000 Mini 1 year subscription for under $400.
After installing and activating Studio 5000 with Logix Designer rev 34, I had to restart the installation link using the same serial number, then I was able to select from a list of previous versions to install. I think I remember the list going back at least to rev 13.