Am I white on black Or black on white? The world may never know

I have many arms but no skin, and hundreds of DIAMONDS but no wealth. I hang upside down all day, yet I never get a headache. I’m born from fire and ice, and I can turn a dark room into a ballroom with one flip of a switch. What am I?

I'm a word of letters six, And with me you can do some tricks. Ready now, let's have some fun. Add an S and I'm more than one. But wait, there's more, you're not yet done. Add another S and I'm back to one. What am I?

An indoor space to encourage sled dogs to go faster, perhaps?

Why Johnny went the extra mile; he missed his . . . .