Can devils or jinn harm human beings, possess them, and enter their bodies? And can they know what is going on in a person's mind without it being uttered, along with mentioning the legal evidence and its strength or weakness?

The possession of a human by a jinn is established. A jinn may harm a human with blows or other means if the human harms them, such as by pouring hot water on them or killing some of them. This might also be mere mischief. This harm does not occur except by Allah's permission and decree. As for jinns knowing what is in a human's mind without it being uttered, this is from the Unseen, which only Allah knows. Jinns eavesdrop in the heavens, hearing a word from revelation, and then convey it to their allies among soothsayers and diviners, adding a hundred lies to it.