"Thanks to all who participated in the brainstorming discussion to get this to work.
As a result of that discussion, the Blender Release team has now set Blender up in such a manner that we can now roll back to previous versions on Steam.

If you need to roll back to or want to stick with a version (back to 2.77),
In the Steam Client Software Library, find Blender,
Right click it and go to Properties
Find the Betas tab and click it
In the Beta Opt-in drop down, you'll find the an entry that will link and download the last stable release for the version selected.

On selection, Blender will go into download mode and replace the current version that is on your computer with the version selected.

Versions use the Appdata information So if you still have the old version configs and add-on in your C:\Users\,username>\AppData\Roaming\Blender Foundation\Blender folder, that will be used.

Unfortunately, we can stilll only download one version at a time, if we want to do so side by side comparisions between version, we still have to download the version we don't have installed from Blender.org

However it is now possible to roll back and stick with versions back to 2.77 on Steam.

This is great for those who have old projects and not want to port the project to a newer version or want to follow old tutorials from start to finish without having to search for moved, renamed or deleted functionality. All one has to do now is roll back to the version used in the project or tutorial."