I'm cut but never bleed, I have teeth, but dont bite, I belong on a ring, but I'm not a gem What am I?

First in round, then square is bound, in triangle form is my last shape found.

I am two-faced, I pass freely between masters; Yet disloyal as I am, all value and desire me. What am i?

I'm present in floors, I roll on them too, Children use me as a toy, adults use me for decor, Children don't need a lot to buy me, adults need much more, No matter how you buy me, I'm always smooth.

I’m soft but firm, a nightly friend, where dreams begin and troubles end. I take your weight without a sound, and hold you gently off the ground.