Kinetela: This mon looks very mediocre. It shares a typing with Gorilax, but has much poorer bulk overall. To compensate it has better but still middling offensive stats. Its speed is pretty middling too and does it no favours. The best tool it seems to have is a very strong Final Gambit, but even then it seems like a mediocre scarfer due to its Speed tier that only lets it tie with Electritar, as well as just generally being pretty weak. Not that great of a mon.
Spinfly: Super good speed, okay bulk for an offensive mon and an attack stat that's workable when backed with Libero. We've already got a lot of Normal and Flying types, but Libero makes this one a sort of exception. I feel like it would be pretty nice against offenses, even though Electritar or Koatric seem like a shoe-in for any of those types of builds. Its movepool isn't too excellent but is good enough, and its low HP actually limits the number of times it can Brave Bird or Head Charge. I think Flash Cannon could be good on this too, even with uninvested base 56 Special Attack, as with Life Orb it prevents Baloon from checking you, generally does more to Mega Chillyte too, especially variants not running much special defensive investment. It also has Lovely Kiss which I think could contribute to this being pretty annoying. Overall this one doesn't seem broken.... just strong and really annoying to play against. It also feels really redundant in my mind with the other Flying types we have, even though I know Libero makes it somewhat distinctive. Even though it plays a lot different from Pidgeotine (another Normal/Flying with Lovely Kiss and Ground coverage) and Ostria (another flying type who also has Protean), I feel like we could do a lot better than this.
Oysteat: Here's another Aquazelle "check" thanks to Immunity. The more I think about this one the more I realize Oysteat struggles to check much of anything. It can check Eartharoo without Secret Sword, if it can keep its health up, matches up well against special Gladiaster and Chillyte, and has a dicey matchup against Aquazelle since its recovery relies on the foe not being behind a Sub, and the fact that Aquazelle can run recovery of its own and beat it down through attrition. Against Chillvark, Koatric, Electritar, Stuneleon, Toados, Voltecta, physical Gladiaster, NP Skeleray (especially variants with recovery), Crazefly, the matchup ranges from mediocre to awful. A special wall that uses Strength Sap as its main recovery is really quite clunky. As a physical wall it doesn't stand out much either compared to Aquatopus. Its best use would probably be Coil + Resttalk actually, since that set can't be worn down by Aquazelle and gives it a much more defined niche, although it kinda removes the need for Immunity. Might be okay but I'm not crazy abou tit.
Glacitile: Yay another Ice type. Hustle can make it decently strong but besides that it doesn't really stand out much at all. Not gonna spend much time on this one as Roulettemons already has 7 Ice types, and even if it was good we wouldn't need another.
Demoon: Even on something with a number of weaknesses like this I think Wonder Guard makes it too strong. Parting Shot is a big part of this that lets it gain momentum and pivot out of bad matchups. It's got really nutty coverage that makes it a handful to switch in on, and its very existence will limit the viability of Choiced mons in the metagame. Even though most offensive mons have at least something to hit this with, the pressure it could put on more defensive teams feels pretty intense, especially if it gets a Sub up. Pursuit Trapping could work, but the best Pursuit user (Ninjoth) is easily OHKOd by Stone Edge or Superpower, making switching in risky. Any potential Pursuit trapper needs to watch out for Parting Shot too. All these traits combined make this mon just way too strong.
In conclusion I feel like Oysteat and Spinfly might be the best choices but honestly I don't really like any of them that much, so you may just see None from me.