Answer:
I occur twice in eternity. And I'm always within sight.
My second is performed by my first, and it is thought a thief by the marks of my whole might be caught.
There is a word of letters three, Add one letter to it and none there’ll be. What is the word?
What has been around for millions of years but is never more than a month old?
One more than a duet.
What is lighter than what it is made of?
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?