Is permissible to buy/sell with non-Muslim?
Yes buying/selling for a Muslim with non-Muslim is permissible as regards what is lawful.
Is it permissible for a father to divide his property amongst his children except one under the pretext that he has paid for the latter`s tuition? This is knowing that his other children were given the opportunity to pursue their education but didn`t because they were educationally poor. Moreover, is he allowed to give his other children who have helped him with growing his business?
All perfect praise be to Allah the Lord of the Worlds. May Allah`s peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
The father should be just between his children as regards gifts, in case they had similar circumstances. However, if any had a special merit, then it is permissible for the father to take that into account to be just. For example, giving his children who have helped in making his fortune and received no reward for that or giving the little ones because they haven`t taken as much as the older ones or giving the sick child who is unable to make a living. The most important thing is achieving justice. Moreover, the father is not interdicted by any of his children, and he is free to do whatever he wants with his money and Allah will call him to account as regards observing justice between his children. And Allah The Almighty Knows Best.
What is the ruling on eating the food prepared by Christians friends knowing that their income comes from trading in alcoholic drinks?
Praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
It isn`t allowed to have the food of the person whose source of income is unlawful. However, if it is a mixture of lawful and unlawful, then it is permissible to have their food. And Allah The Almighty Knows Best.
What is the ruling on reciting verses of the Holy Quran on water, then drinking it?
It is permissible to recite Quran on water, then drink it as a kind of treatment since the Quran heals. Allah, The Almighty, Says (What means): "We send down (stage by stage) in the Qur’an that which is a healing and a mercy to those who believe: to the unjust it causes nothing but loss after loss." [Al-Isra`/82].