'What does that say' challenges you on homographs.
As you will have been discovering, English has a rich range of words that look the same but can sound differently, and/or carry very different meanings, according to their context. How good are you at distinguishing between members of these pairs, or even larger groups?
Answer 1 refers to the noise made by someone's tapping action (a light, repeated knock, such as the sound of a blind person walking along a familiar street and tapping their white stick every so often to check where they are); similarly ~ perhaps with a small hammer ~ in Answer 3.
'Tapping off' a fluid, or 'tapping into' something (physically or metaphorically) means opening a tap to encourage the good stuff inside to flow out, e.g. molten metal from a furnace, or wisdom or advice from a person or group with previous valuable experience.