What is the next number in this matchsticks series riddle?

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?

What has a ring but no finger?

How is the moon similar to a dollar?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

How many words can a pen with half refill write?

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?

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?