Yes, rollback is not admitted if you try to install without unistall.
Use the own steinberg program to uninstall, whithout any problem, then install old version you want.
License will work, and your preferences too, no need to do nothing more.
(If you use any software, as Revo Unistaller or others, that clean the REGEDIT (I supposing you are on windows) DON’T CLEAN ALL, let the steinberg unistall routine works, and you are safe and can restore old version in a minute!)