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

I add 5 to 9 and get 2. The answer is correct, so what am I?

A man is trapped in a room. The room has only two possible exits doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

How can you tell a raw egg from a hard-boiled egg?

Find the missing number in the sequence below:

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

Look at the picture and find out which square is not linked with any of the other squares.

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

There are three Athletes (John, Tarun and Harish) and their individual Coaches (Jacob, Meenaxi and Priyanka) standing on the shore.
No Coach trusts their Athlete to be near any other Coach unless they are also with them.
There is a boat that can hold a maximum of two persons.
How can the six people get across the river?

What is full of holes but still holds water?