Not according to the product specifications. This box is designed to transmit picture and sound and to redirect the sound to a third party device.

I can't judge that. I need the extractor on the Sunrise TV box and it works perfectly there.

Sorry, I don't know and can't find the instructions.

Yes, that's possible, but why not take the audio from the beamer to the system?

A docking station is needed to use multiple screens on a notebook. If the notebook has a USB-C port with video out function, docking solutions can be purchased that support two or even more screens. However, the cheap solutions are only capable of delivering 2 x 1920 x 1080 pixels. Better solutions can also drive 2 x 4K 3840 x 2160 pixels, so I wouldn't buy anything cheap. A third screen can be controlled via the HDMI connection of the notebook. This docking solution can control two 4K 3840x2160 pixel screens via USB-C if the notebook has a USB-C port that can handle video out: Club 3D Club3D USB-7-in1-HUB USB-C > 2xDP/2xUSB/2xUSB-C (USB C)