Answer:
Forward I’m heavy, but backwards I’m not.
Crooked as a rainbow, and slick as a plate, Ten thousand horses can't pull it straight.
People are hired to get rid of me. I'm often hiding under your bed. In time I'll always return you see. Bite me and you're surely dead.
There are millions of me. I am very small but when moving fast I am deadly.
The higher I climb, the hotter I engage. I cannot escape from my crystal cage.
I can only be played on a windy day
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?