It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Find the next number in the series below

21 32 54 87 131 ?

I am soft and cuddly that soothe your heart. But, If you pick my last name I am going to tear you all apart. Who am I?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Count the number of triangles in the picture below:

Four children having five rocks each were playing a game in which they had to throw the rock at a particular solid area in the water. Child 1- Succeeded in throwing three rocks at a solid area but one of the rocks sunk. Child 3 - His aim was so bad that all rocks got sunk. Child 4- He was awesome and none of the rocks got sunk. Child 2 - Was the winner but was struck by a rock in the head and died. Who killed Child 2?

What brings you down but never up?

What number divided by 4 is the same as that number minus 4?

If in a code language, DISTANCE is written as IDTUBECN and DOCUMENT is written as ODDVNTNE, the how will THURSDAY be coded as in the same language?