Software update

Yes, and it's pretty straightforward. I've done it myself on an Ion, to get from a new Beta to an older Release version - and the only difference from a normal upgrade was an extra restart in the process (the rollback needed to uninstall files and restart, then I just "upgraded" from there to the desired SW version).

Although it is possible, I'd add to that it's generally not recommended unless there is some specific reason for needing to do so as newer versions include important bug fixes.