Have a few questions *SPOILERS*
First, let's compare endings. The ending I saw was Leila and her mother climbing though a portal which ends up in Katie and Kristi's house. Leila runs off and after a bit her mother finds her in the basement with a cut on her hand. Leila says something about them only needing a drop of her blood and then shortly after 'Toby' in 'human' form (all you see are weird-looking bare legs) comes from out of frame, kills the mother, and then he and Leila walk out of frame together. This appears to be the standard ending, but apparently there are alternates which might have something to offer.
If Leila and Hunter are the important ones for the prophesy or whatever, what was the point in the other people? For example, did The Marked Ones add anything important to the overarching narrative?
I get that the sixth of June is 6/6, but why 2005? They say in the movie that it's the sixth year, but since there was no year zero the official sixth year of the new millennium is actually 2006. Also, why is the placement of the year in relation to the millennium significant at all, and why is it more important than just containing the number six? This numerology crap is more annoying than the '18 is 6+6+6' in The Marked Ones.
If the demon follows people instead of houses, as is repeatedly said, then why go to the effort to get the family to move to that particular house. I vaguely understand that it has something to do with portals, but I don't especially remember portals being of any importance in the first few films. Also, why not just get someone to kill the family like Katie sometimes ends up doing. Possibly I'm missing something obvious here, but I'm not really getting why so much effort was needed.
What are the rules for demons interacting with the real world? Why get Leila to go down and turn on the gas when the demon could do it itself? Could it not light its own matches? Maybe it couldn't touch the religious stuff, but Leila didn't have to stay after putting it in the fireplace. And they sort of forgot about it after that scene anyway.
Also, why does the demon fly around sometimes but walked around other times? I thought maybe it had something to do with scaring the family, but they usually weren't around while it does this. Feels like it's doing if for the cameras, that is, because it's a movie rather than because it makes sense.