a). Sounds like a very shallow level which goes about N to a collapse. It's very shallow and looking at the gradient, was designed to be a flower-outer. It seems odd to have a level so shallow, if it was a feed for dressing floors, surely, they would have used a bit of a longer pipe and a launder from the engine shaft. It seems unlikely that it was a footway, or access. It had a tyre in it, last time I looked. It heads towards another fenced off square, which appears to be a shaft.
b). There are a number of candidates for your second querie, you'll have to be more precise.
Weirdy Beardies aka Cornwall Mine Explorer's Club meets the first thursday of the month, aka this thursday at The Coppice in lanner. 7:30ish. There are lots of people to chat to about hoels in the ground and where they go and what they were for.