I had never thought of a potential difference between 'porn' and 'porno' until I encountered the following dialogue from Family Guy Season 9 Episode 9(thanks to FumbleFingers for reminding me the correct TV show and episode):
Priest:
Leave this House of God!
Lois Griffin:
But... But I love the Church! It's an important part of my life!
P:
Maybe you should have thought of that before you made a porn!
L:
But Father, I didn't mean - wait, did you say 'a porn'?
P:
Yes.
L:
Oh... Well, that's kind of weird.
P
: Why?
L
: I mean, you either say "You made porn" or "You made a porno". You don't say "made a porn". It just... it hits the ear wrong.
This implies that, as a noun, porn is uncountable meaning pornography in general, and porno is countable meaning a pornographic movie/tape.
Both Merriam-Webster and The Free Dictionary define 'porno' as a perfect synonym for porn. The Urban Dictionary isn't of much help either: the first six definitions are jokes, and the seventh says that it's just another way to pronounce 'porn'.
So,
Is there any difference between 'porn' and 'porno' or not?
Can both be used both as a noun and an adjective? (if yes, provide examples, please)
Can either of them be used as a countable noun? (if yes, provide examples, please)
Are there any differences specific for American, British or any other variety of English?