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

It belongs to you, but other people use it more than you do. What is it?

What's a single-digit number with no value?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

How many letters are in the alphabet?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Can you replace the question mark with the correct number in the below table sequence?