Every words stands for unique digit that makes the arithmetic equation true

SEVEN + SEVEN + SIX = TWENTY.

What are the digits ?

Name a key which is hardest to turn.

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

I look at you, you look at me, I raise my right, you raise your left. What am I?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

Who always enjoys poor health?

Count the number of squares in the picture below.