I have started with short answers, to your various doubts, then I have elaborated my answer to give you clear picture.
Is Moksha the end of samsara[sic]: No, it is not. You can achieve Moksha and still live in samsara.
i.e: the end of reincarnation, the end of repeated cycles of reincarnation.[sic]`: Yes, and No.
Or it is the end of suffering[sic]: Yes it is.
i.e: reincarnation is eternal and there are many Mokshas, each Moksha in one incarnation?[sic]: You can stop rebirth, if you wish once you attain Moksha. Rebirth is eternal only for the people who do not achieve Moksha, or fall back from Moksha.
What if there's no suffering in one's life and no samsara debt and One lives in this very life a rightful life, all this means the end of reincarnation. You have to be authority to judge your own-self. You can't take place of nature of divinity and judge your own karma. Hence, one can not determine the fruits of your own doing. You can only do Karma. Evaluation process is done by higher existence.
I think reincarnation is eternal.[sic]: Again, it can be stoped, if you wish.
Further explanation, to your doubts.
The concept of rebirth/reincarnation exist in Sanatana Dharma, and not in Abrahamic religions.
In the given context "Moksha" simply means "detachment". Detachment of mind frees you from Samsara. Your prospective of perceiving life changes.
You can attain Moksha, while you are alive and living with family.
You can attain Moksha, while you are alive and left your family.
You can attain Moksha, after your death because of the good deeds that you have done or purely by the blessing of saint(s) (if you have served them well), and in some special case it is achieved purely by the virtue of god/goddess' grace (rare).
In Abrahamic religions, salvation either means, the saving of the soul from sin and its consequences or, the eventual entrance to Paradise for the people who die believing in God. Also, in those religions there is no concept of rebirth. You live once and you die once.
In Sanatana Dharma (falsely known as Hinduism), there is no concept of "Belief", or "Salvation", or "Single life".
You know the God "as-is" through one of the four defined elaborated paths:
1) Jnana/Gyan Yoga: Through "Yogkshem" you receive the knowledge gained in past life, or through strenuous efforts in current life you can achieve "as-is" knowledge of God through studies.
Yogkshem: the Knowledge, Mantra Jap, Yagya phala (fruits incurred through Yagya), etc. that you have obtained through your spiritual journey in past lives are protected by God himself and returned to you in current life (Karmic law).
2) Bhakti Yoga: Normally, people think that you have to believe in God in Bhakti yoga and alone that will suffice everything, but Bhakti according to Agama Sashtra means using your emotions along with knowledge that you have incurred so far through various means and put all together and worship your beloved god (Shri Vishu, Mahadev, Krishna, Sakti Devi etc.) to achieve desired results. Yogkshem can be applied here as well.
3) Karma Yoga: You perform good deeds in current life as prescribed by various authentic scriptures. Yogkshem can be applied here as well.
4) Kriya Yoga: It is a higher form of yogic practices which can be learned from authentic yogi(es). Yogkshem can be applied here as well.
Above, explanation is to provide the clear understanding between differences in root concepts of "belief", and "Salvation" compared to "as-is" knowledge, and "Moksha".
Moksha is a "state", it is a blissful state that can be attained after self-realization, self-actualization and self-knowledge. So, it being a state, it does not guarantee that you will remain in that state forever. You can fall back to complexity of samsara, if you are not vigilant or conscious enough e.g. Vishwamirtra sage.
Moksha also gives you option of taking birth again for well-being of common masses, or you can simply avoid taking birth again and submerged with higher existence.
