There are stairs to the cave itself, but inside is a completely natural pathway. Nothing between you and the speleothems except a rope on the ground. Lights are an LED system worn on each individual’s helmet. And about a bazillion glowworms down in the lower levels over a lake.
Not always. I run a commercial tour (approx 5k visitors per annum, so fairly small in the great scheme of things) - one of the things we pride ourselves on is keeping the cave in its largely unmodified state. It’s really special to be able to share that with people.
Yes, generally seen as a last resort to provide access past a squeeze but I know of several caves that have had Kilometers of passageway added to their surveys through the enlargement of a single point.
Just FYI, I’ve not had much luck with cracked Bitwig - its clever enough to detect the protection is bypassed and blasts static for a few seconds every few minutes. Not usable. Granted this was a year or three back, so things may have changed.
West Coast of the South Island of New Zealand.