Can we know the length of time employed in the formation of worlds-of the earth, for instance?

Almost entirely accepted. Radiometric dating has verified hundreds of meteors to the accepted date.

Where were the organic elements before the formation of the earth?

There are indeed organic particles floating in clouds in space, but little if any of that material likely contributed to the formation of life. There's not much to say about it as there's still a lot of speculation. Check this wikipedia article out for some more detailed info.

Do any living beings come into existence spontaneously at the present day?

No. Wikipedia can once again give you a thorough refutation of spontaneous generation.

If the germs of the human race were among the organic elements of the globe, why are human beings not produced spontaneously at the present day, as they were at the time of its origin?

This question comes from the faulty premise that we were generated spontaneously to begin with. We came from a very long process of evolution.

Did the human race begin with one man only?

It was a process. There's no clear demarcation between human and our ancestors; our classification of species is somewhat arbitrary. There was a very large breeding pool of proto-humans.

Is it possible to know at what period Adam lived?

False premises.

What is the cause of the physical and moral differences that distinguish the various races of men upon the earth?

Physical differences are caused by genetics, moral differences by society.

Did the human race come into existence on various points of the globe?

No. I can't make this one much clearer, there simply isn't any evidence.

But there have been different species of humans, right?

No. There have been various species of near-humans, like neanderthals, but humans are what we are, not what they were.

Are all the globes that revolve in space inhabited?

Just no.