Noodle is a 6 legged dog and it doesn't die. Stated by the author herself in this interview:
https://www.vox.com/culture/22901210/nona-the-ninth-cover-reveal-tamsyn-muir-interview-locked-tomb-series
"I do want to note that there’s a beautiful dog on the cover, and that dog is the most important dog in the universe. I realize saying this compromises my artistic integrity because an unsaid central question in the book is, “Will anything go wrong for this dog?” But I lost my dog back in December, and I just want to say, nothing goes fundamentally wrong for the dog."
At least two characters have some degree, mostly stemming from being in bodies that aren’t their own. And a third much later on is similarly upset by the form she took without consent
A nun features in the John chapters, who discusses some religion. The size and location of the human soul features.
In universe religion features by nature of a character being called god, but discussions are largely interplanetary and geo-political and about the morality of necromancy itself rather than real world religon.
There are entities of unclear origin that some in universe refer to as devils. They are not associated with hell, which does not appear in the metaphysics of the series.
No, but their is suspicion of domestic violence, and an authority figure repeatedly advertises a shelter that for domestic violence survivors to a main character due to a misunderstanding.
There are multiple characters publicly set on fire for spectacle, in a public execution. We do not meet these characters, nor do we see them on fire directly, so we do not know if any are women, however, it is likely some are women.
Someone sexually harrases the childlike character in an adults body and is quickly driven off and not seen again. It is unclear if they had any indication she was not an adult.
Many mentions and discussions of characters burning alive, some fairly graphic.
A character burns alive on the page fairly late in the novel but is unharmed after.
A character has potentially fatal micro-seizures. Different symptoms are described thrice in the span of two chapters. At one point, another character is mentioned to hold them down.
No minors are sexualised by the medium, which is what this category asks in it's description. A minor character who is never seen again sexually harrasses a character who is childlike in an adult body, and is quickly driven off by another character.
A character is using a body that is not hers, and two characters share a body consensually. The main character is described as "waking up in a stranger's body and not wanting to give it back".
One of the characters is a female soul living inside a male body. There is a scene in which someone else, perceiving her as a man, believes she is predatory/a pimp. However, this is not due to her being trans-coded.
The secondary protagonists go out of their way to avoid calling an amnesiac by either of two names they think the mind in her body may have had in the past, not least because she is not that person any more.
There is some confusion over a returning character and whether they have taken an additional name to go with a title or replaced it, and whether this was of their own free will.
Towards the end, the amnesiac is called by the body's name, due to ignorance of events, and the returning character is also called by their old name.
https://www.vox.com/culture/22901210/nona-the-ninth-cover-reveal-tamsyn-muir-interview-locked-tomb-series
"I do want to note that there’s a beautiful dog on the cover, and that dog is the most important dog in the universe. I realize saying this compromises my artistic integrity because an unsaid central question in the book is, “Will anything go wrong for this dog?” But I lost my dog back in December, and I just want to say, nothing goes fundamentally wrong for the dog."