Name a key which is hardest to turn.

In the below-given picture of a pretty girl, there is something wrong. Can you find out what it is?

One day, I thought of ways that can be used for creating a palindrome. So I decided that I will turn into a larger number by adding the reversed digits to the original number and keep doing it till I finally obtained a palindrome.

I am not sure if this process will always result in a palindrome eventually but I was able to produce a four-digit palindrome. Can you guess my starting number?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

No one wants to have it, but if one got it, he does not want to lose it. What is It?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

Spot what is wrong here in below Picture?

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

I was born in a small house and I live in it all alone. No windows and no doors have been assigned to my house. The only way I can go out is by breaking through the walls of my house.

Who am I?