Answer:
I know a word of letters three, add two and less there will be.
I cannot be felt, seen or touched; Yet I can be found in everybody; My existence is always in debate; Yet there is a style of music named after me.
These are believed to be found at the end of rainbows
What is something yet nothing, but if you fill it up it will disappear?
I occur twice in eternity. And I'm always within sight.
How can you tell when a mummy has a cold?