Answer:
A mile from end to end, yet as close to as a friend. A precious commodity, freely given. Seen on the dead and on the living. Found on the rich, poor, short and tall, but shared among children most of all.
When young, I am sweet in the sun. When middle-aged, I make you gay. When old, I am valued more than ever.
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
Look into my face and I'm everybody. Scratch my back and I'm nobody.
It's equally comfortable in an orchestra and a geometry textbook. What is it?
Special abilities and brightly colored underwear are all you need to be one of these.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?