Yes, it is possible with a splitter for 2 microphones. I work like this with two Sennheiser clip-on mics and the new GoPro Hero7 Black. The quality of the GoPro 7 is also very good without microphones and records stereo or room.

No, unfortunately not, the adapter was designed exclusively for GoPro cameras.

For example, can I connect the Nikon ME-1 there and make stereo recordings?