What Am I Riddles

Question: At the end of a long dark cave there is a monster made of lead. Be careful. One twitch of the finger and you will release it.

What is it?

Question: I can be half without getting thinner.
I can shine with no fire.
I can be hidden but never taken.
I can stay dry while moving the ocean.

What am I?

Question: I can be dropped from the tallest of buildings and survive,but drop me from the smallest ship and I won't.What am I?

Question: I'm written with two letters, said with one and seen with two.What am I?

Question: What type of cheese is made backwards?