Answer:
What has four fingers and a thumb but is not alive?
Cut the wrong wire and it goes boom
What freezes after it is heated up?
I can be as thin as a picture frame but my insides have many things you can see.
It goes up and down the stairs without moving.
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?