Answer:
When young I am sweet in the sun. When middle-aged I make you gay. When old I am valued more than ever.
I have three feet but no arms or legs
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
If you lose me you may cause people around you to lose me too.
found at the back of the book.
Give it food and it will live, give it water and it will die.