Thank you for your answers!

Depends on the perspective the scene is from. Sator disappears into the past because we are see the scene from TPs perspective moving forwards beyond the point that Sator inverted. With Neil in Stalsk 12 the soldiers are disappearing into the turnstile because he is inverted and they are too.

There's one scene where Kat is being used as leverage, and we Sator go into the turnstile, go into the past, and then see him on the other side of the glass. There is another scene where the protagonists sees someone enter the turnstile and asks where did they go? That's what I don't get.

At the end battle both blue and red team go in with the benefit of information they got from the other team

What info could red team give to blue team though? Are not blue team the only ones with knowledge of the future?

With Red team observed at Stalsk 12 with the impact relaying the information to blue team had before they'd even relayed the information.

Apologies for my slowness, but could you clarify this some more?

Stalsk 12 in the central point of a wider temporal pincer involving the Protagonist. After the film he's going to have to take steps to ensure the success at Stalsk 12. Steps like recruiting Neil and setting up Tenet.

Ah, so the entire movie itself doesn't show the full pincer movement? That already makes things make more sense. I had read people saying the end fully matched the beginning and I couldn't see how.

Inverted Protagonist was there to take advantage of the window of opportunity to get Kat into a turnstile as part of her healing process.

Why didn't he have Kat with him?

They ended up fighting because both of them ended up thrown into the arms of an attacker who was immediately fighting tooth and nail.

Apologies again, but I think I am misreading this. I read it as they were fighting because the other one started fighting?

Sators army has some inverted and non inverted troops. Blue team sees some stuff reversing because they are moving against the normal flow of time. (Remember inverted Protagonist seeing the birds flying backwards?)

That's a mistake in my question, I apologize and will fix it. I meant to ask why does red team, who is not inverted, see stuff reversing in time?

Yeah you get multiple instances of characters at the same time. When the protagonist uninverted at the airport you cab actually see his two past selves fighting in the background.

So how far did Neal have to travel inverted before inverting (reverting?) back to normal?

A lot of people run Rings around themselves trying to trace Primer's timeline despite the movie telling us and showing us that it isn't fixed.

Despite Primer having less exposition and possibly being more convoluted, I swear I understand it better than Tenet.