I’ve been in a number of caves in my life, and none has had vertical walls and a perpendicular ceiling. I suspect something is amiss with at least the pictures.
I agree. It looks like a mined shaft.
You are right - those are mine shafts or something definitely man-made. As for Ice Age, that may be just conjecture on their part, else there were mining operations going on 15,000 years ago - not really a stretch as no one has figured out exactly who mined all the copper in the Michigan UP or where all the copper went.
Ah, now we know where the Egyptians got those rocks for the pyramids.