Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

Two friends were stuck in a cottage. They had nothing to do and thus they started playing cards. Suddenly the power went off and Friend 1 inverted the position of 15 cards in the normal deck of 52 cards and shuffled it. Now he asked Friend 2 to divide the cards into two piles (need not be equal) with equal number of cards facing up. The room was quite dark and Friend 2 could not see the cards. He thinks for a while and then divides the cards in two piles.

On checking, the count of cards facing up is same in both the piles. How could Friend 2 have done it ?

Suppose you are a girl candidate and sitting in an interview. Suddenly the interviewer asks you, 'What if one morning you wake up and find out that you are pregnant?

How will you reply to such a question?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

What does this Rebus Picture means ?

A little girl goes to the store and buys one dozen eggs. As she is going home, all but three break. How many eggs are left unbroken?

Bopanna was working on a murder case when he received a message about the location of the murder weapon.
The message was encrypted as below.

"deb mitciv eht edisni neddih si nopaew redrum ehT"

Tell me the location of the murder weapon.

You are stuck on an island where you have nothing. You find four pieces of paper somewhere on the island. What will be your strategy to escape from the island safely?

PS: No other resource is available to you on the island, neither can you build anything.

Cristina was born in 1888. She just had her 30th birthday today how did that happen?

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?