Which number should replace the question mark?

Can you decipher the below rebus?

PBLUESAISNUERSES

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

How could a baby fall out of a twenty-story building onto the ground and live?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?

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?

I got a bee but no honey.
got an eye but am still blind.
got a sea but no water.
got a tea but no coffee.
got a why but no answer.

What Am I?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

John speaks the truth only once a day in a week. Below are a few hints for you:

First: Days are Sunday, Monday and so on.
Second: One day he says, "I lie on Monday and Tuesday".
Third: On the next day, he says, "Today is either Thursday, Saturday or Sunday".
Fourth: On the next day, he says, "I lie on Wednesday and Friday".

Can you identify the day on which he speaks the truth?