Answer:
The warmer I am, the fresher I am. What am I?
I am a key that is playful. What am I?
Born of sorrow, grow with age, you need a lot of me to be a sage. What am I?
Poor people have it. Rich people need it. If you eat it you die. What is it?
What has roots that nobody sees and is taller than trees. Up up up it goes and yet never grows?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.