Should I uninstall my old versions before installing the new versions??

There is no direct conflict between the software versions here.
The main consideration is space. You'll definitely want to remove the old versions in order to free up space.

If you are updating a previous version then remove the old one after you've finished installing and running the new one.

If you are installing from a full version DVD (not just an updater) then you can remove the old versions either before or after.