Long Riddles and Answers

Question: Fifty is my first, my second is the third in fourth, and my end is the end of an ending. With a nut I become a nut that isn't, and without one I move.

Question: It's hard to give up.Remove part of it and you still have a bit.Remove another part, but bit is still there.Remove another and it remains.What is it?

Question: Flora killed several thousands of people without mercy. Afterwords, Flora disappeared and was never seen again. Yet the police never pursued her.Why?

Question: These are the three lives of mine:
So gentle I soothe the skin,
So light I caress the sky,
So hard I crack rocks.

What am I?

Question: I can pogo on the moon, but not Mars. I can pogo on this table, but not on a stick. What can assure us to be able to pogo on objects at all times?