Four riddles from a video game

I recently played this game, Fran Bow. This is a puzzle game, and thus has a lot of riddles.

But here are the four that I favor among all. I am four different things. Who or what am I?

1. I’m cold as I am, but if you use me… I’ll be burning hard.
2. I’m shiny as the sun but I’ll never burn you. Perhaps a sour smile I’ll get you.
3. Flow, flow cold blooded son. Let your body dance through the rising stream.
4. Light and hollow, I’m the freedom of birds and the pen of men.

Note that in each question, I am different.