Revealing mistake: At the start, just as Moreau rides up the stone road leading to the monastery up ahead, before he passes the two guards we can see that it's a flipped shot - note the backwards license plate number.
Continuity mistake: During Nadya's escape from the monastery, there are exterior shots of Nadya through the windshield and there's nothing hanging from the rear-view mirror, but in the interior shot (viewed from the back seat) just as she swerves away from the red car, there's a small cross on a cord which is hanging from the rear-view mirror.
Chosen answer: This is a sequel. The only major difference from the first one is the Devil's human appearance.