Answer #1) Whatever area your floor covers in an open space without any floor obstructions, if you have a cat.

Answer #2) It will take milliseconds for the liter water to be on the floor, after the cat has found the dish.

Answer #3) 1 Second, after the fat cat jumps off of one end.

Answer #4) None, if you decide to superglue or velcro tape the keyboard to the desk to avoid problem #3.