Answer:
There is someone, and there is always another, for without the other, there wouldn't be one
My first is an insect; my second is a border; my whole puts the face in a tuneful disorder.
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-legged am I. Name me and see me at home in the sky.
It is weightless, you can see it. If you put it in a barrel it will make it lighter?
There is a puzzle which can be asked all day with a different correct answer each time. What is the puzzle?
What is so fragile that saying its name breaks it?