What does this rebus puzzle means ?

I am something people love or hate. I change peoples appearances and thoughts. If a person takes care of them self I will go up even higher. To some people I will fool them. To others I am a mystery. Some people might want to try and hide me but I will show. No matter how hard people try I will Never go down. What am I?

In the Wild West, you are challenged into a death match by two bounty hunters nicknamed Golden Revolver (GR) and Killer Boots (KB). You accept the challenge. None of you want to waste any of the bullet and so a certain rules are laid down:

1) All of you will shoot in a given order till the last man standing.
2) Each of you shoots only once upon his turn.
3) If any one of you is injured, the other two will finish him off with an iron rod.
4) The worst shooter of all (which is you) shoots first and the best one shoots at the last.

Now, how will you plan things if you know that you hit every third shot of yours, KB hits every second shot and GR hits every shot ?

Name a key which is hardest to turn.

If eleven plus two equals one, what does nine plus five equal?

What does below science rebus mean?

Ag Ag Ag
Ag SPOON Ag
Ag Ag Ag

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

Most people think of me as money. But when they find me in the water, they won’t get any money out of me. What am I?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?