A man donated a burial plot, but before registering it in favor of the Ministry of Awqaf and before burying anybody there he said that he didn`t want to donate it and planted it. What is the ruling of Sharia on this?

All perfect 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.

If he had endowed it as a cemetery, then he can`t take it back, even if he didn`t register it in favor of the Ministry of Awqaf. If he said: "I have endowed this plot as a cemetery, then it becomes an endowment." However, if he didn`t endow that plot-but it was his intention to do so-then he is allowed to back down. And Allah The Almighty Knows Best.

Should the Zakah (obligatory charity) giver tell the poor recipient that this is the Zakah of his money?

No, he shouldn`t. But, the Zakah giver should make an intention in his heart that it is the Zakah of his money when paying it to the poor. And Allah Knows Best.

What is the Islamic ruling on adoption, and what is the legal window through which a person can be kind to an orphan girl, attend to her needs and raise her as his own?

Kindness to an orphan entails a great reward from Allah, but adoption is prohibited and invalid. Therefore, it is permissible for the aforementioned person (for example) to make his brother`s wife breastfeed that girl so that he becomes her uncle by suckling provided that he informs her that she isn`t his biological daughter.

What is the ruling o associations (Whereas a person who have money buys a commodity for a person and  and gets a profit on it)?

It is permissible for a person to buy a commodity for someone's else and have a profit/loss on it