All tours other than the basic tour require prior reservations and approval by the tour operators. They are not for everyone.
The Toughnut tour is mildly strenuous. It involves scrambling and climbing some near vertical ladders. It is for the more adventurous who don't mind getting dirty. Anyone who is claustrophobic or has issues with heights would not enjoy it.
The two extreme tours are just as they say, "extreme" and are only for people who are fit and capable of several hours of sustained exertion. The reward is seeing some areas deep underground that are rarely visited. The toughnut tour is a prerequisite.
Tom's Geology Info / tom@mmto.org