I travel all around the world but always stay in the corner. What am I?

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

It has horns but can’t beep. It is like to bleat but It is not a sheep. What is it?

A thief is convicted in Mexico. He gets the death penalty. The judge allows him to say the last sentence to determine how the penalty will be carried out. If the thief lies, he will be hanged, if he speaks the truth he will be beheaded. The thief tells the last sentence and to everybody's surprise some minutes later he is set free because the judge cannot determine his penalty. What did the thief say?

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

Spot 5 differences in two Christmas tree below:

I am the fastest animal but cannot climb the tree. What am I?

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?