Answer:
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?
I have thirteen hearts but no body or soul.
What is black when you buy it red when you use it and gray when you throw it away?
I have Eighty-eight keys but cannot open a single door.
I go around a yard but does not move.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.