Answer:
When young, I am sweet in the sun. When middle-aged, I make you gay. When old, I am valued more than ever. What am I?
I have cities with no people forests with no trees and oceans with no water.
I am in the past, never in the future. I don't exist, but have existed. I saw what you saw, and this is what I will ever see. What am I?
I am the only thing that always tells the truth. I show off everything that I see. I come in all shapes and sizes. What am I?
The more you take away from me, the bigger I shall get. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.