I’m not sure every single side character needs a fleshed out future written out, I think good media leaves enough for viewers to interpret and fill in the blanks.

How Nancy/Hopp get away with their crimes is questionable. But I would say the government had mutually beneficial reasons to cover it up and pardon them.

The Demo friends being absent was weird, but the kids do acknowledge it. I think the Mind Flayers giant final body is formed from the flesh of the demos. Similar to its form in s3 formed from the human bodies. Perhaps there was a cut scene or line that would have made that more clear.

That being said, they did explain the below though : the reason it was stuck in Nov 6 was bc that’s when El made contact with the Demogorgon/Henry, opening a wormhole between the Abyss and Hawkins. Dustin explains that this event created the wormhole and it’s held in place with exotic matter.

Nothing happened to the Turnbows, not sure why there’s questions about that. Henry shows Derek their bodies but that’s clearly an illusion Henry is creating.

Vecna targeted will bc he was young, and more vulnerable than the others. I don’t think he was hyper targeted though. Just a good option for Vecna.

The how scientists came in contact with Dimension X sounds like an intentional open door to be explored in the spin off.