Answer:
You can read it both ways, I wearΝΎ One way it's a number, reversed a snare.
What is pronounced like one letter, written with three letters. And belongs to all animals?
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
What can touch someone once and last them a life time?
Hands she has but does not hold. Teeth she has but does not bite. Feet she has but they are cold. Eyes she has but without sight.
You use it between your head and your toes, the more it works the thinner it grows.