Is the son of the sister by breastfeeding considered a mahram in Islam, and is it permissible for a woman to go for Hajj with him?
Everything that is prohibited by lineage is also prohibited by breastfeeding. The son of the sister by breastfeeding is considered a mahram, just like the son of the sister by blood, and it is permissible for him to be her mahram for Hajj and Umrah. And Allah Knows Best.
Is it permissible for a financially capable woman to pay the Zakat to her sons or one of them?
It is permissible for a mother to give her children from zakat if they are eligible to receive it, even though she is obligated to provide for them. This is based on the saying of the Prophet Muhammad (PBUH) regarding Zainab, the wife of Abdullah Ibn Mas'ud (may Allah be pleased with them): "Your husband and your children are more deserving of your charity" [Al-Bukhari]. And Allah Knows Best.
My husband wanted to sell a piece of land that was his own, but his father insisted that he transfer the land in his (the father’s) name so that he could sell it at a higher price. Then, my husband and his father would split the price. After my father-in-law sold the land, he denied everything and refused to acknowledge my husband’s right. My father-in-law passed away a year ago, and my husband’s brothers divided the inheritance, refusing to acknowledge that this land was a trust held by their father for my husband until it was sold. Are they sinful for knowingly denying that the land belongs to my husband, and what is the ruling on praying against them?
All perfect praise be to Alalh, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
Among the rights of the deceased upon their heirs are: preparing them for burial at death, settling their debts, returning people’s rights to them, executing their will, and then dividing their estate. What was mentioned in the question falls under the rights of others, even if they are among the heirs, and the deceased is not absolved of it unless it is returned to its rightful owners. This is because Allah, Almighty, forbids consuming others' wealth/properties unjustly. However, do not give up on seeking a solution by involving righteous and well - respected individuals who may have influence over them, in the hope that Allah guides them to goodness and correctness. As for supplicating against them, the prayer of the oppressed is not rejected, even if the oppressed person is not a Muslim. And Allah knows best.
If someone bought a car from an interest-based bank and then sold it to another person, does the second person bear any sin if they use the car's price to pay the installments owed to the bank?
When the buyer purchased the car, it became their property, and the price became their responsibility. The bank acts as the seller's agent for receiving the payment. Therefore, there is no sin on the second buyer, God willing, as long as the bank does not impose an increase in the amount if a payment is delayed. And Allah The Almighty Knows Best.