Why Aeroplane windows are round?

There was a competition where the contestants had to hold something. At the end of the event, the winner was a person who had no hands or feet. What was it that the contestants had to hold?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Sherlock breaks into a crime scene. The victim is the owner who is slumped dead on a chair and have a bullet hole in his head. A gun lies on the floor and a cassette recorder is found on the table. On pressing the play button, Sherlock hears the message 'I have committed sins in my life and now I offer my soul to the great Lord' and followed a gunshot Sherlock smiles and informed the police that's its a murder.

Why did he think so?

What does the below image rebus riddle means ?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

Can you count the number of squares in the figure below?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

Yesterday I fell from 30 feet high ladder but I don't get hurt. Why?