Is there any way of finding out the store generated ProductID prior to submission of a new app? It used to be that we could create a store app and (without submitting) get its allocated ProductID and then paste this into our WMAppManifest.xml in order to be able to set up Facebook social login that requires the app ProductID.
Not possible as far as I know. You can submit the app as hidden so no one downloads it, get the id, then add the Facebook integration and then submit it again.