Who always enjoys poor health?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

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 ?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

I cry without having a voice.
I fly without having wings.
I bite without having teeth.
I whisper without a mouth.

Who am I?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

How is a fly different from a mosquito?

There are five men, let's say Tarun Harish Lavesh, Manoj, and Manish. All of them have a dot mark on their forehead. They can't see the dots on their forehead but can see the ones on others. The owner of WHITE Dot is an honest person and will never lie, while the owner of BLACK Dot always tells the lie.

This is the statement from Tarun Harish Lavesh and Manish:
Tarun: 'I see 3 whites and 1 black'
Harish: 'I see 4 black'
Lavesh: 'I see 3 black and 1 white'
Manish: 'I see 4 white'

What colour is the dot on each of Tarun Harish Lavesh, Manoj, and Manish's forehead?

The barber of Town shaves all men living in the town. No man living in the town is allowed to shave himself. The barber lives in that town. Who then shaves the barber of the town?