Short Riddles and Answers

Question: I can be seen and heard miles away, only show my position for a couple of seconds, but if touched it can kill you instantly.

Question: There is a thing that if you put in water and get out, put it back for about 2 minutes, you won't see it again. What is it?

Question: If you're looking for something sweet I know what to do.
But if you don't like heat I'm not for you.

What am I?

Question: There is an ancient invention still used in some parts of the world today that allows people to see through walls.What is it?

Question: what can walk on 4 when they are born, walk on 2 legs when they are older and walk on 3 when they are old uncles and aunties?