I moved into a house where the previous owners had installed beech
wood strip flooring throughout the ground floor. The beech is oil
finished (matt).

I have a few questions which I would be grateful if somebody could
advise me on:

1) Is it possible to remove black stains caused by water soaking into
the wood?
2) Theres a nasty stain caused by dripping oven cleaner in the
kitchen! Is this beyond repair?
3) Can the flooring be treated with varnish/wax or something to keep
water out -I would only want to do this in the kitchen and hall which
is most at risk of wear and water
43) Any advice on cleaning, improving the wood. Buffing? Mopping?
Rubbing in oil?

Thanks!