Answer:
What is that which, though black itself, enlightens the world without burning?
I'm light as a feather, yet the strongest man can't hold me for more than 5 minutes.
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
Slayer of regrets, old and new, sought by many, found by few.
Neither bought nor sold but more valuable than gold. It is built but not by hand. What is it?
What did the piece of wood say when he saw the screwdriver and screws approaching?