Answer:
I am black when you buy me, red when you use me. When I turn white, you know it's time to throw me away. What am I?
What goes up and down stairs without moving?
If you break me, I'll not stop working. If you can touch me, my work is done. What am I?
I am a seed with three letters in my name. Take away the last two and I still sound the same.
Take off my skin I won't cry but you will. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.