Answer:
I cost no money to use, or conscious effort to take part of. And as far as you can see, there is nothing to me. But without me, you are dead.
No matter how little or how much you use me, you change me every month.
A caribbean shape that makes ships disappear
I have four legs but no tail. Usually I am heard only at night.
The itsy bitsy teeny weeny yellow polka dot variety is quite popular.
I can only be played on a windy day
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?