Fixing it, laying it, and what the substrate does.
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Because this stone is heavy and rigid and does not flex, so it takes the movement of the building rather than absorbing it. The substrate has to be flat enough for the back of the slab to bed, and the fixing has to allow the panel to move without the stone cracking.
Mechanically anchored where the wall is tall or the substrate is not solid, bedded in mortar where it is a masonry wall. Either way the substrate has to be flat to the tolerance of the fixing, and the panels have to be able to move with the frame behind them.
On most floors, yes, and in a wet area absolutely. A stone floor is bedded or fixed to the base, so the base is what keeps the water out of the building. The membrane is part of the floor and not a detail to be added later.
A floor laid as slab takes about a day per 100 square metres once the substrate is ready, and a panel wall takes longer because every panel is set, numbered and fixed. The part that is not ours is the substrate, and it is normally the longest part of the job.
Ordered by how many questions each one holds.