Answer:
The little pink nub that helps rectify mistakes.
It weighs next to nothing but no one can hold it for long. What is it?
The part of the bird, that is not in the sky, Which can swim in the ocean and always stay dry. What is it?
What has been around for millions of years but is never more than a month old?
It is something you will never see again.
I am a rock group with four members. All dead one was assassinated.