Which number should replace the question mark?

What's the only room from which no one can enter or leave

Here is what you have to do. You have to throw a ball as hard as you can but it must return back to you even if it does not bounce at anything. Also, you have nothing attached to the ball. There is no one on the other end to catch that ball and throw it back at you.

How will you do it?

Identify the movie name through below Rebus containing Pi Mouse and coconut tree..

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

What has 13 hearts but no other organs?

using four eights (8) and a one (1) and one mathematical symbol , create the number 100

A detective visits his friend John just to discover that John's neighbour Dr Jacob was murdered. Dr Jacob, who is a mathematician wrote the murderer's name in a code word "Hcqtfz". There were five suspects
1. Ajit
2. Pankaj
3. Ganpat
4. Deenu
5. Hariya

The Detective was instantly able to find the murderer.
Can you?

I am thinking of a five-digit number such that:
The first and last digits are the same, their submission is an even number and multiplication is an odd number and is equal to the fourth number. Subtract five from it and we obtain the second number. Then divide into exact halves and we get the 3rd number.

What number I am thinking of?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?