Rarely known secrets about Hinduism
The advent of the prophets of Abrahamic religions including Abraham, Jacob, to Jesus Christ and Prophet Muhammad were mentioned in the bhavishya purana, a compilation of early prophecies of Kali Yuga as told by Veda Vyasa nearly 7000-8000 years ago.
Hindus are not descendants of Adam and Eve and hence original sin and related concepts do not hold good to a Hindu as long as the gotra of the person can be traced back to a rishi.
There is a presiding deity/angel to every yuga. Kali purusha who is the presiding demonic angel of this immoral age of darkness (kali yuga) is verily the Satan mentioned in Abrahamic religions.
The actual names of Adam and Eve are Adama and Havyavati. The are the progenitors of the mlechha race (the non-aryan race). Their story is mentioned in the prathisarga parva of bhavishya purana. And there is more to their birth. In fact it also mentions the reason behind the birth of Adam and Eve. During the nearing end of dwapara yuga, Sanatana Vedic Dharma, the eternal truth of life, was shining in a blaze of glory. The dharma of kali yuga is immorality, wickedness and disbelief in the existence of God.Kali Purusha/Satan was finding it impossible to spread immorality when righteousness was present in people. That was when he performed a penance to the Lord underneath a western sea for thousands of years. He questions the Lord after pleasing him with his Tapas, "Oh Lord! How can I follow my duty to spread immorality in the minds of men when dharma is shining like a fire in every direction?".
The Lord replies to his prayers saying, "As long as I stand on earth in human form (as Krishna), it is impossible for you to spread evil. however it is your duty to do so and hence I grant you a boon that you can influence the minds of men after I leave my mortal frame. In addition to this, I will also create two people named Adama and Havyavati on a distant land. The brother and sister will be virtuous by birth. You can try, provoke and influence their minds to indulge in immoral sex. If they comply to your deception, they will fall from my grace since it is a sin for a man to breed with his sister. Thereon, they will become progenitors of the mleccha race, who will bear upon their original sin. This race will not follow the Vedas which is the word of God. They eat uncouth food without any regulations. Not being able to control their senses, they will indulge in forbidden relationships not sparing even mothers and sisters without following the matrimonial code. Since they are sinful in nature, you will be able to spread evil in the era that follows by largely influencing their minds. However, I warn you of the fact that these are not my abandoned kids. I will affirm my existence at various times revealing the Sanatana Dharma, the word of God, to those who yearn for it with a true heart, no matter how sinful by birth, one who's mind is fixed upon the Lord, him, you cannot influence. This is my boon to you."
And later on comes the birth of Adama and Havyavati and their progeny from thereon.
The stone that Jacob thinks as a pillow and dreams of climbing up the heavens is actually a Shiva Linga. Jacob performing the bath to the stone, decorating it, applying paste to it, is actually a Vedic ritual called Maha-Rudrabhishekam. It is verily the same stone that is worshiped in Mecca Masjid today as the Kaaba. The zamzam river well water that flows there is actually Ganga. People honoring it go around the stone in circles which also has a vedic connection. It is termed as pradakshina in Sanskrit.
All spoken languages of this world trace their existence back to Sanskrit. Indian languages have the most appropriate grammar and lipi(script) because they are direct descendants of Sanskrit. Even ancient languages like Hebrew and Aramic are less close to perfect when compared to the current version of Indian languages which is why English being a mixed descendant of Greek, Latin and other ancient languages is weird in its own way. No one knows why "put" and "cut" are pronounced differently inspite of having similar lettering. This is also the main reason why some Christians question the originality of interpreted English verses to equivalent Hebrew verses of the Bible. In fact, Arabic is comparatively old when compared to others and hence it might be the closest bet at performing linguistic research. When the Arabic Quran version of the Adam, Evestory is compared to that bhavishya purana, one can find closely related words.Havyavati in Sanskrit becomes Hawwa, Mleccha becomes Malekkha, et al. I've once heard one Arabic researcher jape the English people for not having the slightest idea of the term "Hallelooyah" which they often use in their prayers. He claims that it is an adulterated version of "Allahlooh Allahlooh". Not sure about this but makes sense in some way.
The blame for this misunderstanding should not be put on the interpreters but on the original languages like Hebrew which were not very wholly perfect. Sanskrit is older than Hebrew but some folks still understand it because it is perfect. When a language is perfect in its grammar and lipi, it preserves itself through centuries and millenniums though being subjected to minor changes.
Jesus Christ was a reincarnate of Dhruva, a young kid mentioned in theBhagavata Purana who performs penance to Vishnu at a very tender age of 5 and worships him as his father. The Lord pleased with his penance grants him permanent residence in the highest of the highest heavens in the Brahmaanda, called the Dhruva loka, which is why Jesus as his reincarnate shows paternal love towards the almighty and affirms his disciples residence in his heaven, theDhruva Loka upon living a virtuous life as suggested by him. The GoddessMaaya during the birth of Krishna, at an other time also worshipped as Kanyaka Parameshwari of Vaishyas has reincarnated as Mary, the mother of Jesus Christ. This truth is told by Lord Dattatreya himself. One can read the Sreepada Sreevallabha Charithamrutham to know details regarding these facts.
This is also why it was decided by the Lord, that Jesus being a very highly elevated soul, a divine incarnate was born unlike the other prophets. He has free of sins though being born in the mleccha race because he is not born out of sexual union.
Jesus as Issah Massihah (addressed with many other names) is also associated with the Natha Sampradaya (the Avadhoota cult of Dattatreya) where he trained under Naths and various Buddhists in between the age of 13 and 30. There are documented proofs and manuscripts in Buddhist Tibetan monasteries that depict Jesus living in the Indian-Tibetan subcontinent. Irrespective of people's opinions about the life of Jesus Christ, Bhavishya Purana clearly depicts King Shalivahana's meeting with Jesus Christ in Nothern caves of India, where in the latter affirms like this upon the King asking him "Who are You"? I am Isha Putra, the Son of God, kumaari garbha sambhavaam, the one born of a virgin, mleccha dharmasya vaktaram, the Guru of Mlecchas. The King bows down before him and asks him the reason for his birth.
Jesus Christ replies to him saying "O king, when the destruction of the truth occurred, I, Masiha the prophet, came to this country of degraded people where there are no rules and regulations. Finding that fearful irreligious condition of the barbarians spreading from Mleccha-Desha, I have taken to prophethood by the Lord's order"
The above mentioned are not really secrets per se, they are merely less known facts. Hinduism is a vast subject. It has many things in it ranging from science and mathematics to God and spirituality. It is really a fantastic area of research to those who are interested in knowing about it. There are still a myriad more secrets within Hinduism which one can know only when they dive deep into it.
Based on the question posed, I've just tried to share with you what I know. I am not a propagator of any religion and I do not intend to speak less of any. I've just shared what I've learnt and understood so far. So I hope that I wouldn't be attacked by abusive comments from religious fanatics.