[LG G8X ThinQ Questions & Answers] Dathaniel:
You'll have to take my answers with an understanding that a bit of it will be speculation. You see, I do not own an LG G8x Dual Screen. I do, however, own a Korean LG V50 Dual Screen, so I can provide some insight and provide you with some answers

This will not work. The Dual Screen can flip open to 360°, putting it behind the device, but two things are going to prevent you from using it like you've asked. The secondary screen, at least on the V50, shuts off when the case reaches this position. It actually stays on for most of the arc, only flicking off at about 350°, but it does render itself unusable on the back of the device. Even if this can be changed in the software of the G8x, the second problem is that in this position, the 360° opened Dual Screen, facing the rear of the device, will block the backside of the primary device, obscuring the cameras. The Dual Screen will only face the rear of the device in this 360° opened position, at which point the primary cameras will always be blocked.

It mirrors the primary display. I haven't tested what happens on any of the handful of dual screen "wide mode" compatible apps, but I would imagine it would still only show the right pane on your mirroring device. However, I do speculate that it could be possible to mirror the dual screen instead, if you could pick out which activity in the system is the begin mirroring command and then set a widget or Tasker profile to automatically initiate it. There are some system apps that do not allow you to move it over to the Dual Screen display, and the cast screen subsetting menu is one such app. However, I believe that it might be possible to cast the secondary screen instead if this were the active screen at the time that screencasting began. As far as casting both, I doubt this would every be possible. Most apps can only exist on one screen or the other at a time, per install. (There are ways to install multiple copies of an app, but they become entirely separate apps as far as the system can tell.) The screencasting service is one such app, which can, in theory, only exist on one display environment or the other. Maybe it could be possible to get two separate screencasting apps and run one on each display, but then you would need to cast to two different devices. I guess I'll go with a hard "maybe" on this one.

I will assume that nothing happens. You see, the supporting software to run the Dual Screen is preinstalled on the V50, on the primary device, and mI assume this will be the same on the G8x. The Dual Screen Settings subsetting menu is present in the system menu. The Dual Screen's Home Launcher is installed on the primary device. Connecting, say, a Galaxy s10 will likely cause nothing to happen, because the s10 would not have any software or drivers to interface with the Dual Screen Accessory.

That said, I am interested to see if my Dual Screen capable V50 will be able to interface with the G8x Dual Screen Accessory, and I will test this as soon as I get the chance.

Likewise, I'm interested to see if anyone can reverse engineer the drivers and allow the Dual Screen Accessory to be used with non-native, or non-LG devices. As soon as everyone realizes that the Dual Screen form factor is the future, and this silly foldable display hype bubble deflates, I think we'll end up with some competent developers working on the issues.

This is an interesting question. Do you mean just using a USB c female to USB c male cord, to plug the device into the dual screen, but at a distance? I don't see why not. To plug it into a splitter so that you can plug in another device? Probably unnecessary, as there is a port with some style of USB c passthrough on the case, but it might work, as long as the device isn't trying to draw a bunch of power from the device. The screen is powered through this port, and you could easily exceed the power output limits of this port.

And if you're asking about the possibility of using some kind of a splitter to try to Daisy Chain a couple of dual Screen Accessories to a single primary G8x device, that's crazy enough that it just might work, if you can figure out the power issue.

The Dual Screen Accessory does not have a Haiti motor of it's own, but the haptics work from the primary device when you are working on the dual display.

Hide, Probably, to some extent. The V50 insides

Includes the option to hide it in the LG apps and preinstalled apps, but it doesn't usually work on third party apps. I haven't sought a third party "notch hiding" app, because frankly, the notch doesn't bug me at all. And on the V50, it is much more pronounced. But there's no way to "turn it off" even in the Dual Screen, where it is entirely non-functional. The notch exists because of a lack of pixels being there at all. The Dies that they use for the manufacture of the screen are responsible for the notch, which LG Included "unnecessarily" in the G8x so that they could simply have their two screens come from the same supplier, same batch, so that they will have Identical specs and color science. There's no way to turn the pixels there back on or anything, but there might be something you can do about turning the whole top strip of the phone into a dark, notch hiding, fuax bezel or whatever. I dunno, if the notch is a problem for you, I don't know what to tell you. I'd guess that you've not had a device with a notch before. Because they really aren't a big deal. Especially not these little teardrops.

Of course, individual milage may vary. But if the notch is a turn off for you, don't let the fear of the notch dissuade to from your interest in this device. What LG is doing in the space is revolutionary. Be the first you know to try it, and you'll see exactly why I think Multi Display Tech is the future of smartphones.