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

A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

What does a man do only once in his lifetime, but women do once a year after they are 29?

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

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

A boy collects white seashells from the sea and brings them home every night. When he has enough of them, he decides to sell them to a trader.

The trader is ready to buy the shells and he asks the boy about the quantity. At this, the boy starts calculating. He has a giant box that contains 3 mini boxes. Two of them have another mini box inside. If the giant box can hold 50 shells, how many brown shells can he sell to the trader?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?

What brings you down but never up?

The horse jumps over the king.
Strangely there is absolutely no scratch on him.

Can anyone explain, how is this possible?