I have a bunch of Facebook applications that will have to use the same set of Open Graph concepts (actions and objects)…
Do I need to define them repeatedly for each app or can they be defined in one app and reused in the others?
The tutorial seems a little bit ambiguous about that.
I´d say it will not work, because of the different domains (you do have to set an URL in the developer settings). Also, afaik it´s somewhere in the Facebook rules that you are not allowed to use one and the same app for different pages/purposes.