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 the guardian to give Sadaqa (voluntary charity) from the money of the orphans?
It is impermissible for the guardian to donate from the money of the orphans because he is entrusted with the safekeeping of that money, and is prohibited from donating it.
Is it permissible to thin the eyebrows or remove them and draw in their place?
Thinning the eyebrows, removing them, and drawing in their place—known as Namas—is prohibited. The Prophet (peace be upon him) cursed those who do it. And Allah Knows Best.
By slip of the tongue, my son cursed Allah. It is worth pointing that he has concluded his marriage contract recently, but haven`t consummated the marriage. What is the position of Sharia on this?
All perfect praise be to AllahThe Lord of The Worlds and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
This person must return to the fold of Islam by uttering the two testimonies of faith and making repentance to Allah from all acts that lead to disbelief. Also, he must make a new marriage contract because the old one was dissolved after he had committed this act of disbelief. Moreover, since there is no waiting period for his wife, then she is in state of Talaq ba`en baynona Soghra (Minor irrevocable divorce); consequently, she can get back to him only by a new marriage contract. And Allah The Almighty Knows Best.