Whatever the "circular aperture" portion is, there seem to be two more on the front of her belt and at least nine on the device she operates here. Emitters of some sort, perhaps? Behave, gentlemen.
Kaplan wasn't replaced because of favoritism or some backstage politics. One quick look at IMDb shows that he's attached to two films - Star Wars Episode VIII and Arms and the Dudes, the latter of which is currently filming. He simply wasn't available when the movie entered pre-production. There's no mystery here.
I doubt it. More likely it's a "nod" to the actual existence of such holsters in the real world and in thousands of movies previous to Star Wars.
Yes, but all of them were in Black & White. Also, there was this thing known as a "Mighty Wurlitzer," which was used to conceal the fact that the movies had no sound of their own.
^^I don't follow. So Kirk and the landing party are checking out crashed wreck, find crates of new uniforms and Kirk decides "let's wear these" despite the fact everyone's already wearing perfectly good uniforms?
First of all, I admit my theory is unlikely to be true. But if it is, there would be some plot justification. I'm thinking of ENT's Mirror Universe arc, where they board the hijacked Defiant in spacesuits, and later change into the TOS uniforms they find there, just for the sake of comfort. So, just for example, the Nu crew are on or in the crashed ship when the decayed surface beneath them gives way, and they plunge into a ready room full of dank dirty water; Spock and Scotty sheepishly pull themselves out, and Kirk tells them, "You guys stink - go change."
But then presumably a crashed ship doesn't have working showers, so even if they change their clothes, they'd still stink. And why would the ship have different duty uniforms than the Enterprise's?
Well, the comics do have the uniforms from the previous two movies having been in circulation for twenty years (Captain April and his crew are wearing them in a flashback scene) meaning they would have been introduced as replacements to the uniforms we saw on the Kelvin.