Do you mean default to open .prproj when you double click on them?
IF that is what you want. Right click on a file > Get Info > Look for Open With, set to the app version you want. Also click change all. Now when you double click a file it will launch that version.
Note that this will try to open all the project files in that version so if you have a newer project file it will not open. But when you want to open that is the newer version you right click again and go to Open With there.