Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

Identify the hidden meaning behind this picture?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

If eleven plus two equals one, what does nine plus five equal?

Jack was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

How many triangles are there on the puzzle below?

In a secret society, a buried chamber can be accessed only via a secret password. The password is seven characters long and comprises of just letters and numbers.

You find a code that can help you in cracking the password. The code says "You force heaven to be empty".

Can you deduce the password from that?