cassava or Manioc is the staple food of the people live in rainforest.
The answer is the door.
It is a riddle. Riddles are the puzzles where clue about anything is given in like a poem and we will have to search for the answer form the clues.
It is said that it can hold a prisoner which is a door or gate.
It can also set a prisoner free, which is also a door or gate.
It swings around, and not a tree. So, it is pointing towards a gate or door.
It is saying that it keeps secret which is a door.
3 heat zones are
1) torrid zone ( 23.5N TO 23.5S)
2) TEMPERATE ZONE ( 23.5N TO 66.5 N) & (23.5S TO 66.5S)
3) FRIGID ZONE ( 66.5N TO 0N) &(66.5S TO 0S)