Good Riddles

Question: A five lettered word, I'm used to make bread.
Remove one letter and I'll burn you instead.
Remove two and do this to your stew.
Mix that around and a good drink we will brew.

Question: A man orders a coffee and finds a fly in it. He sends it back and gets another one. But he quickly discovers that they gave him the same coffee that had the fly in it.

How did he know?

Question: Whoever makes me can hear me, but nobody else can.

What am I?

Question: Scientists are trying to figure out what is between Heaven and Earth.What is it?

Question: There is a prison with 100 prisoners, each in separate cells with no form of contact. There is an area in the prison with a single light bulb in it. Each day, the warden picks one of the prisoners at random, even if they have been picked before, and takes them out to the lobby. The prisoner will have the choice to flip the switch if they want. The light bulb starts off.

When a prisoner is taken into the area with the light bulb, he can also say "Every prisoner has been brought to the light bulb." If this is true all prisoners will go free. However, if a prisoner chooses to say this and it's wrong, all the prisoners will be executed. So a prisoner should only say this if he knows it is true for sure.

Before the first day of this process begins, all the prisoners are allowed to get together to discuss a strategy to eventually save themselves.

What strategy could they use to ensure they will go free?