I'm still curious to know if it is possible to back out Slackware upgrades
if in current and want to go back to previous current then you have to have that mirror and do it just like the upgrade text reads. slackpkg does not go by version it goes by change log and and package list. If it is different then it see it as a upgrade. Had to do this many times.
pretty simple matches your /var/lib/slackpkg/pkglist if going back from current to stable you do the up date . I keep a few mirrors on my system so I can just do it as a upgrade.