What is the value of potential energy of a mango on a tree before it fells?

Answer 1

m g h is the potential energy on the branch if you define h, height, as zero on the ground.
All you can say about potential is difference. You have to pick a spot where you call it zero.
In the case of a fall out of a tree, you usually say zero at the ground. However if it fell in a
hole you could say zero at the bottom of the hole.