TeenCorn I just remember that there was a systemd thing that didn't make the process as smooth as one would like but yes it definitely possible.
Ah yes, I can't remember the details or find the post about it, but there was something that could disrupt the update process, true.
Anyway, what was your original intent again, @Axios? I think I don't fully understand why you want to install an old iso in the first place. Solus installed from an old ISO should be mostly identical to one installed from a new ISO, after the updates have been applied.