
Question: How could the Erumpent the size of a whale escape out of Newt's case without Newt around, without his help (magic)? Can Erumpents shrink themselves like Occamies?
Answer: This might actually be a valid mistake. The exit of the suitcase is depicted as being inside a hut, at the ceiling. A savanna creature like that would not even consider that to be a route it might be able to take, because that requires (sorry for the pun) out-of-the-box thinking.
Perhaps that would be true for a non-magical creature; however, there are numerous references in the Wizarding World canon to magical creatures have human-like cognitive abilities (Kneazles are one prominent example), so perhaps Erumpents fall into the same category.
I agree under normal circumstances the creature wouldn't try to escape. However, as Newt pointed out, this creature was in mating season and was looking for a partner; which is why she went to the zoo as there were the closest creatures she sensed to herself. Animals going out of their natural habitat when they sense a potential mating partner is a natural survival instinct real animals do. As real animals do this, it makes sense this creature would do the same thing as a real animal.
As said elsewhere, the exit is depicted as in the ceiling. Erumpets aren't displaying any intelligence beyond that of a bull or rhinoceros. Climbing out through a roof hatch is not in their behavioral patterns, mating season or not. A bull won't climb a ladder, no matter how many cows are on the roof.

Question: What was the liquid in the big containers that Harley Quinn and Joker jumped in?
Answer: The same unknown acid/chemical combination that created the Joker in the first place.

Question: What happened to Psylocke after the movie? Would you say this indicates an appearance in another upcoming X-Men film?
Answer: Psylocke is purposefully shown literally just walking away after the dust has settled. She could very well show up in another film somewhere along the line but nothing has been confirmed as of yet.

Question: How did The Red Queen shrink The Mad Hatter's family into the size of ants?
Answer: She probably forced them to drink "Pishalver" which is the potion that will make one shrink.

Question: When Dr. Strange gets into the accident near the beginning of the film, why didn't his car's airbag deploy? Wouldn't such an expensive car have all kinds of standard safety features?
Chosen answer: The airbag did deploy. However, the deployment occurred when the car first crashed and we see the accident from the outside, so we can't see it. Once we get a shot of the interior, you can see the airbag is sticking out from the steering wheel, but (unlike what some movies would show you) airbags deflate very rapidly after a crash, so you may have missed it.
But if the airbags did deploy, then why did he have such major injuries? Wouldn't the airbags have made what happened to his hands less severe?
I don't think so. I watched it again recently and I think I saw the car's speedometer crush his hands while they were still on the steering wheel, while the airbag deploys from the centre of the steering wheel, nowhere near his hands.
Often in real life, when air bags deploy from the steering wheel, they force the hands off the steering wheel resulting in the hands hitting the windshield. Damage to hands, wrists, and lower arms are common.

Question: Who is it that Bruce sees in his dream/vision while waiting for the file to be decrypted? It seems like it might be the Flash, given his time/dimension-travelling powers, but it doesn't look like Ezra Miller and seems to be wearing some sort of armour.
Chosen answer: It is Flash. He is wearing armour because of whatever has transpired in the future. He often wears an armoured suit in dire circumstances in the comics.
Also, if you look at the bottom of the image frame you can just make out the Flash icon on his chest piece.

Question: While there were various characters being held in a sort of "suspended animation" entwined in the "canker man's" roots/webs, only one was set free (the foster care agent), why? (01:20:35 - 01:24:25)
Answer: We only see her released, but the implication is that the others were, too.

Question: Why did Shere Khan kill Akela?
Answer: It was a threat to Mowgli, hoping to lure him back in grief and to save the younger wolves from the same fate.
Answer: Shere Khan was angry that Akela would not turn over Mowgli to him. It was retaliation.

Question: How is Emma sitting on the horse and cart when she is lighter than air? I have watched the movie a few times and cannot see anything like a belt around her waist, but any other time she is sitting, she has been seen buckled down.
Chosen answer: At several points throughout the film, there are instances where her powers of air are used only as a plot device, so the extent of her powers is somewhat unknown. Therefore, it is possible she is able to make herself sit on the cart without floating, but other times isn't.
Answer: This is a movie mistake because when she's at dinner, she has to wear a buckle to hold her down. And I don't see why she wouldn't be wearing one on the carriage too.

Question: I am confused as to what really happened. Was the entire series of movies a fantasy of Reggie's like Mike said it was? Was the planet taken over by the Tall Man like the other reality showed? Or are we left to our own imagination on which reality was real and which was not?
Chosen answer: This film is infamous for its confusing to follow narrative, owed to the fact it was originally intended as a series of shorts rather than a linear structure. As it stands it is up to the viewer to decide, however the post credits scene seems to suggest one world is real as Reggie plays no part in the scene.
Chosen answer: Erumpents cannot change their size, however the suitcase is itself enchanted to allow objects of any size to enter and exit its magically expanded interior. Newt's presence is not required for this.
Phixius ★