I've been playing this demo (with cheats because I'm not really "playing this for reals", I'm just curious) and the new areas (castle and underground, haven't made it to the ghost house yet) do seem original.
This one may be legit, but the only way we know is if Carol confirms it.
Carol seems to be very reclusive, he doesn't respond to e-mails a lot (considering people keep begging him for demos...). However, cheat-master-30 did actually manage to contact him a few times.
That's how we got the confirmation about the collab with EXTRA not being true (it was obvious though, Hell Mountain was just recordings of three different Super Mario LD stages edited together - "ファイヤーロープ クレバス", "クラッシュ タワー" and the Mortamor from Dragon Quest VI boss - to look like one level) and how 9.5 didn't exist.
Even if it isn't actually Carol's, I'd like to see whoever did this make a hack. Maybe cut down on the difficulty a bit though, the stages are kinda neat. I kinda liked the YI pipe maze segment.
The autoscroll segment reminded me of raocow's "What the Hell" hack and some of his collab levels ("further over there", "Enough! RUN AWAY!" "trial of iron", "Rupture in Reality", "murder death place zone"), though, but with more manageable difficulty.
I did find another VIP level. I think it's also from VIP1, but my memory is foggy.
The World 8 level name translations are so lame though:
Battleship Halberd → Metaknight's Keep
Airship Graveyard → Ultima's Keep
Dark Castle → Demon's Keep
Dragon's Hole → Dragon's Keep
Mirage Palace → Darklich's [sic] Keep
Showdown! Bowser's Castle → Bowser's Keep
Originally posted by Buried Alive
We will prob see a lot new ASM in The Final Battle and maybe a lot reused and new bosses in Luigi Castle.
Peach Castle → Peach and Poochy boss, Goddess Peach boss
Brutal King Mario (top left skull in World 9) → rematch with Bowser and the Koopalings (due to the MM3 capsule room graphics), Luigi boss
Luigi Omen → battle with Shinryuu and Omega, final battle with Queen Zeal boss (possibly Lavos boss too?)
Remember, Carol said that Luigi wasn't the final boss.