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 sequence

1, 2, 6, 21, 88, __?

What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

What is the coolest letter in the alphabet?

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

John can eat 27 chocolates in an hour, Jacob can eat 2 chocolates in 10 minutes, and Jolly can eat 7 chocolates in 20 minutes. How long will it take them to share and eat a box of 120 chocolates whilst playing Chess?

What has no start, end, or centre?

What does below pictogram mean?