The needs of the same human being may differ at different stages of life. Can there be one Dharma for all stages?

Is there one dharma preaching for all stages of life (or stages of evolution) in Buddhism? or are there many?

There are many dharma preachings relevant to life stages.

Buddhism teaches Five Niyamas

In Kamma Niyama, it says every action has reaction. So don't do to others what you dislike.

There is one Dharma for all, however one may emphasize certain aspects of Dharma to take on certain challenges. For instance, some Buddhist teachings will prescribe certain types of meditations for certain temperaments.

The problem with trying to have a different Dharma for different life stages is that it assumes that every person faces the same challenge at any given stage in life, and this is simply untrue. People's challenges are a function of their genetic dispositions, circumstances, stage in life and so on.

Having said that, there very well may be broad themes that come into play in the stage of life. For instance, in old age, issues of health, impending morality and even irrelevance can come into play. However, it's dangerous to focus exclusively on those themes as how they manifest as challenges is still based on the individual.

Furthermore, even if one were to focus on those broad themes, the Dharma would remain the same, one would simply shift one's energies to different aspects that seem most suited to the theme. For instance, how does the theme of mortality factor into one's ego-lessness? Would something like increased death contemplation be appropriate? What about if one is concerned with physical appearance at a certain age? Would contemplation on the unattractiveness of the body be appropriate here?

But this comes back to different temperaments; entering a life stage (along with one's other factors) could be "reduced" to a shift in temperament, with the appropriate shift in emphasis on the practices involved.

On an unrelated note, what you ask seems more in line with Hinduism, which acknowledges different practices for different life stages, but that's not relevant here. I just thought it interesting given the common religious mileu from which both arose.

The needs of the same human being may differ at different stages of life. Can there be one Dharma for all stages?

Yes there can be one Dhamma for all.

The Dhamma taught by the Buddhas is timeless and does not change. These rare beings discover the path for themselves, they discover an ancient path, after which they teach it to other beings.

The Dhamma is always the same. The Four Noble Truths do not change whether one is 5, 30 or 90 years old.

There is though, different approaches to the Dhamma, depending on what age a human being has.

If one is 5 years old, then a more simple and fantastic approach might be used. For example one uses in greater deal the stories from the Jatakas, to illustrate the different path factors such as ethical conduct.

One might also approach it from a school teachers angle as Crab Bucket has done. He used clay to form dhamma wheels and drawings of the Buddha surrounded by animals. Ven. Yuttadhammo has made a video-series on how to do Metta meditation for kids. In the videos he speak very slowly, calmly and simply. It works really well for kids.

So in other words. If one is pretty young in age then the complexity of the Dhamma, such as the technicalities of the Abhidhamma might not be the best approach:)

If one is 30 or 90 years old, there are many different approaches. The best way to explain this, is to look at the different affiliations of Buddhism and then find an affiliation or several affiliations, that fits ones own understanding of the Dhamma. In the end, they all lead to the same goal, Liberation.

Ultimately, to understand the Dhamma, one has to practice meditation. In the meditation one will truly understand that the Dhamma is timeless and always the same for all ages and stages.