Hello, cleaning of the products is easy, a damp and then a dry cloth. the first import table has an open grain, so using any wax or oil will change the look dramatically. The round table could (if needed) be cleaned with a soft sponge and dish soap as it has a stronger finish.

The first photo looks like a good candidate for sanding until the spots and stains are removed ...hoping to achieve a fresh clean exposure of the wood and then decide if it needs a stain and protective coating ...the second table if it is used for dining will need less sanding .....just to remove anything that will interfere with the acceptance of stain...as to stain...that has to be decided on whether you want to change the color ..or preserve the natural shade..any stain is best applied in very light coats until you achieve a color you like...water base products are always easier to work with... clear coats are available in flat finishes that will dry much faster and will not darken over time ...all of these projects are easy DIY with the right products...and if carefully applied in thin coats