What always comes into a house through the keyhole?

In the picture that is attached with this question, you can find a square which comprises of four little squares inside it. Consider this square to be made with matchsticks. You have to remove two matchsticks such that only two squares remain instead of five.How will you do it ?

Can you place six X (crosses) in below board without making three in a row in any way ?

There is a bag which have 21 blue balls and 23 red balls. You also have 22 red balls outside the bag. Randomly remove two balls from the bag. * If they are of different colors, put the blue one back in the bag. * If they are the same colour, take them out and put a red ball back in the bag. Repeat this until only one ball remains in the bag. What is the color of the sole ball left in the bag ?

I have teeth but i don't bite. Who Am I ?

Can you Find and name the hidden bird in the picture below ?

Alpha is Beta's sister.

Gamma is a Beta mother.

Delta is Gamma's father.

Tango is Delta's mother.

Then,

How is Alpha related to Delta?

I am 5 letters long.
My first two tell you who I am
My first 3 could be a medicine
My last three reversed could be a young boy.
My 4th, 3rd and 2nd in that order could be a fruit drink.
If you have me you may hang me round your neck
WHAT AM I ?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

Our product and our sum always give the same answer. Who are we?