Question: This may seem simplistic, but what happened to the police who were meant to arrive in 14 minutes?
Answer: If the police arrive in 14 minutes, they would be dead and killed by their doppelgängers - Red, Abraham, ombre, and Pluto.
Question: What was wrong with Rachel's sister Zelda? In the flashbacks it shows the older sister as having a twisted spine and being in bed. But what was wrong with her? Was she crippled?
Answer: In the original film, she has a condition called "spinal meningitis," which is an infection in the fluids and membranes around the spine and brain. The disease in real life can cause a range of effects including severe joint and back pain, weight loss, light sensitivity and even brain damage. The implication in both films seems to be that we're not really seeing the "real" Zelda, but more of a monstrous version of Zelda based on Rachel's memory as a child.
Question: When Eddie takes a face full of projectile sludge from the leper, is there any significance to the song "Angel of the Morning" playing, or was it just a random attempt at a joke?
Answer: I think it's more of an attempt at a silly joke, juxtaposing the insane imagery with a tender song. But I've also seen the suggestion that it was an Easter Egg/reference to the book "The Langoliers," in which the song is mentioned. (And given the "It" films have some general Stephen King Easter Eggs referencing things from his other books, that makes sense).
Question: Just after Chucky kills Shane, why did he say that it was for Tupac? Since he wanted Andy to be happy, shouldn't he have said that it was for Andy?
Answer: I wouldn't read into it much more than just a joke: Chucky heard that joke earlier when the kids in the street were trying to make him do things for their cell phone cameras. So he just re-used it later as he often does in the movie.
It was a joke that some kid said when he had the Chucky doll.
Answer: Yeah the kid said that so Chuckie said it too.
Answer: Chucky's A.I. enabled him to learn from others and through experience. Chucky was repeating what the neighborhood boy told him to say ("This is for Tupac"), but Andy's reaction to Chucky stabbing the stuffed unicorn was obviously negative - Chucky would have learned that stabbing someone would not make Andy happy. Hence, Chucky was demonstrating what he learned from Andy's friend/acquaintance and said, "This is for Tupac" (not "This is for Andy").
Chucky might have also thought that some kids view "This is for Tupac" as funny and an appropriate thing to say, but Andy did not because he stopped him when he was stabbing the stuffed unicorn. Also, Chucky didn't know what "Tupac" was or meant. That is, Tupac would not have been recognized as a person's name, so he would not know that he could substitute another person's name, such as by saying "Andy" instead.
Question: Why would Cliff and Ronnie just let themselves die killing zombies when they could've driven off to seek refuge?
Answer: It was in the script that they would die. Ronnie stated he knew it would end badly because the director gave him the full script ahead of time.
Question: Spoilers: When Simon's corpse is discovered flayed apart and hanging, it looked like some of the organs suspended above him (possibly his lungs?) were still moving a bit. Was he still alive at that moment?
Answer: Yes, that is the impression that is given. He is still alive.
Answer: They were delayed or killed. When the family was given the 14 minute estimate it was before anyone, including the police, realised the extent of the problem.