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

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

What is so fragile that saying its name breaks it?

It belongs to you, but other people use it more than you do. What is it?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.

Solve the following series:
AZ, GT, MN, __, YB

You have to fill the below given grid in a manner that every row and column contains the digits 1 to 6. Also, make sure that the squares that are connected with each other must contains the same digit.

The centre of the third figure is empty. What digit should fit inside?

Take one out and scratch my head, I am now black but once was red. What am I?

Replace the question mark with the correct number.