No matter how grave your sin is, the forgiveness of Allah, The Almighty, is greater. So, you should not despair of His Mercy, nor should you lose faith in the vastness of His Forgiveness.
The Prophet (saws) says:
“By the One in Whose hand is my soul, if you did not commit sin Allah would do away with > you and bring people who would commit sin then pray ...
To answer your first question, I’d recommend reading this article
Did the Prophet (pbuh) maintain his ties with his uncle?
Despite his enmity, crimes and tyranny against the Prophet (pbuh) and the Muslims are undeniable, but in response, the answer is no because of two reasons:
Allah (SWT) says: “It is not fitting, for the prophet and those who
The rule is you can't have two sisters as your wives at same time.
Yes, it is permissible to marry the sister of one's former wife, on condition that the ‘iddah of the first wife has ended. The evidence for that is the verse (interpretation of the meaning):
“Forbidden to you (for marriage) are: … and two sisters in wedlock at the same time”