Personally, I don't believe Islam or Christianity are covenants but offshoots from my faith that have missed the mark. From my point of view, the Noahide laws are what you are supposed to follow and we're the custodians of the Torah.
I can not see how or why you connect Islam with Christianity when there are no similarities between them at all
as for the other point: where in the OT does it say it was revealed by God to all nations?
if it is from God, how do you explain the countless mistakes in it, the first page as an example?
no Muslim nor Prophet Muhammad, nor the Holy Quran says that islam is a new religion, or deny any Prophet or Book from God :
2:41. And believe in what I have sent down (this Qur'an), confirming that which is with you, [the Taurat (Torah) and the Injeel (Gospel)], and be not the first to disbelieve therein, and buy not with My Verses [the Taurat (Torah) and the Injeel (Gospel)] a small price (i.e. getting a small gain by selling My Verses), and fear Me and Me Alone. (Tafsir At-Tabari, Vol. I, Page 253).
2:91. And when it is said to them (the Jews), "Believe in what Allah has sent down," they say, "We believe in what was sent down to us." And they disbelieve in that which came after it, while it is the truth confirming what is with them. Say (O Muhammad Peace be upon him to them): "Why then have you killed the Prophets of Allah aforetime, if you indeed have been believers?"
2:136. Say (O Muslims), "We believe in Allah and that which has been sent down to us and that which has been sent down to Ibrahim (Abraham), Isma'il (Ishmael), Ishaque (Isaac), Ya'qub (Jacob), and to Al-Asbat [the twelve sons of Ya'qub (Jacob)], and that which has been given to Musa (Moses) and 'Iesa (Jesus), and that which has been given to the Prophets from their Lord. We make no distinction between any of them, and to Him we have submitted (in Islam)."
The evidence that there is life after death is in the Tanakh.
what is the source of Tanakah?
what kind of lefe and where will it be?
Do you only derive meaning in your life because you will go to Paradise? That's very sad.
I do not derive anything. I follow what my Creator told me through His Book and Prophet.
I posted a thread about (the Fall) in both the OT and the Holy Quran. the answer is there in detail.