score:9
This ticket is valid for the full trip from the airport to Neuendettelsau. Actually, it would be valid for an arbitrary single trip that lasts at most 240 minutes, starts at the airport and goes no further than 8 tariff zones (as defined on this map).
Unfortunately, it seems to be impossible to buy VGN tickets for single tickets in advance online, it says so in the FAQ.
You can buy such tickets from the red vending machines that are present in all train/metro/tram stations or from bus drivers. It seems that at the airport there are vending machines that accept credit cards (German article), but I am not sure whether this is possible in general. Besides with the VGN app you can also use the app of Deutsche Bahn, which among other features allows to buy VGN tickets.