Do I need a previous version installed to install an upgrade?
Upgrades do not require any previous version of Finale to be on the computer when installing or when running. If you have a new computer it is not necessary to put all or any of your previous versions of Finale on it, only the ones you need.
Also, once you have the upgrade on the computer, you can feel free to remove the previous versions, as this should not affect the performance of the new one.