Regardless of the position of any tiles on the pool wall The water level should be about 3 or 4 inches / 75-100mm above the top of the skimmer vein before the skimmer basket or at such a level that it does not suck air through the skimmer. of you have a suction side floating pool skimmer you can let it get as high as you like and as long as it is sealed properly as low as you like.
The water level needs to be maintained at the middle of the skimmer opening or center of the tile line.
To replace the decorative tile border on a concrete pool, the pool will have to be drained. The old tile needs to be taken off and a new tile with waterproof grout or concrete can be installed. The pool should dry for a week or so, before it is refilled.
No. The tile resisist a water line stain. While paint does not.
No the pool doesn't "have" to be drained. Are you replacing all the tile or just making a repair? Small repairs can easily be done by lowering the waterline to just below the tile. There are also new methods of cleaning tile to restore it to near it's original look. If you are changing the tile your tile setter will probably drain the water.
One way would be to install drain tile in the yard around the pool deck to carry excess ground water away from the pool.
It is not likely, but it depends on what material the walls are made out of. Mud, probably not, but tile yes.
Use a phosphate remover in the water and this will dissolve and return the oils back to its natural state. This will control all oils in the water and clean tile water lines in a pool.
A water proof tile adhesive, available at your local hardware store.
Yes, Water should be replaced to normal operating level ,Which would be halfway up the opening of your Skimmers. Normally Center of tile line On 6 Inch tile bands or 3" below the bottom of your Coping.
You are not cleaning the tile or water line each week with a tile cleaning brush and pole. You are not maintaining water quality and sanitation requirements. You are not shocking the pool either with liquid or other shock treatment or both often enough. Neglect? If it is on the tile line it is also in the pool and equipment and nooks and crannies ~ you just can't see it yet. You, I would presume, are also not maintaining your pH or Total Alkalinity. k
Yes, if you want uneven and broken tile. You should level the floor first.
tile Definitely tile!