Can you replace the question mark with the correct number?

What month of the year has 28 days?

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?

What can you hold in your right hand, but never in your left hand?

How many letters are in the alphabet?

A man is lying dead in a field where no one is around. His head is split open and his legs are disfigured. Near to him, there is an unopened package. No living organism can be found anywhere at the crime scene.

How did he die?

Can you write down eight eights so that they add up to one thousand?

Rearrange the letters in "new door" to make one word.