I am not sure if every old version stays available. However I had to binary search through versions of their VR tools once because only a few versions ran on my

I am not sure if every old version stays available. However I had to binary search through versions of their VR tools once because only a few versions ran on my dev. system. The normal steam UI doesn't really expose the versions or provide an option to prevent updates, so the beta workaround might be necessary to tag these versions for end users.