How is hardwood flooring fastened down over a concrete slab. This is the
real oak that is then sanded and finished.

If an oak floor, such as the above, has been refinished once, can it be
sanded and refinished again for a third go-round?

If a natural colored oak floor that has been refinished previously is sanded
out, can it be stained a darker color?

Thank you in advance.

Roger