There is not really a history of agnostics. Agnosticism is a Greek word meaning "without knowledge". Agnostics do not feel like there is enough evidence, one way or another, to prove or disprove the existence of a god and other supernatural phenomena. There have been agnostic views for as long as atheistic views, and religious beliefs have been around.
Agnostics by their nature dont believe in anything as they feel they are not equiped to understand reality./
Agnostics do not believe anything about God. Agnostics do not believe in any type of religion.
There is no recognized 'leader' for agnostics. However, a fair number agnostics are also interested in secular reasoning and philosophy, so many of the great philosophers of the ages (Socrates, Hume, Kant, Descartes) are read and debated by some agnostics. There are also a number of vocal agnostics/atheists who are in the public limelight a great deal, including Richard Dawkins.
All countries.
31.4%
That isn't a simple question to answer. Not all agnostics necessarily believe the same things. So, some do, some don't.
You seem to be lumping all agnostics together into one uniform mindset. The reality is that agnostics, like in almost any group of people, all have their own separate thoughts and opinions. So I'm afraid that your question really doesn't have much of an answer.
They can be either Atheists or Agnostics.
agnostics
The Boy Scouts of America's official position is that atheists and agnostics cannot participate as Scouts or adult Scout Leaders in its traditional Scouting programs. - Wikipedia
There is no reason to expect all agnostics to have the same answer to that. Obviously the world came to exist some way. If you believe you can explain exactly how and why, then your answer works for you. Your answer might not satisfy everyone.
No, there are Sikhs, Jains, athiests, Christians and agnostics.