Hello, Thank you for your purchase <3
The template is on GDevelop latest version, so make sure to update your GDevelop to latest version (GDevelop → Home tab → Click on "About GDevelop" in the Bottom left screen → Check for updates)
the error (SetString Variable extension is missing) is most likely because you are on old GDevelop version, in the new GDevelop version we got new variables actions/conditions.