Answer:
What kind of cheese is made backwards?
I start new then become old. Start clean but be one dirty. I usually start big then become little.
I come in different colors and shapes. Some parts of me are curvy some are straight. You can put me anywhere you like but there is only one right place for me.
What can go up a chimney down but canβt go down a chimney up?
I'm not a bird but I can fly through the sky. I'm not a river but I'm full of water.
I am rarely touched but often held. If you are smart you'll use me well. What am I?