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

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

Can it be possible to build a house that has all its four walls facing towards the South?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

Decode below rebus
D
N
A
T
S , D

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

You need to pick one entry from pot A and one from pot B to have a perfect match. Can you do it?