All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Allaah, The Exalted, chains the (rebellious) Jinn and they may retain their disbelief in Him as is the case with human beings who witness the signs proving the Oneness of Allaah, yet they refuse to believe in them. Allaah, The Exalted, says (what means): {… And if they should see every sign, they will not believe in it. Even when they come to you arguing with you, those who disbelieve say, "This is not but legends of the former peoples."}[Quran 6:25]
Please refer to Fatwa 86963 about the devils being chained during the month of Ramadan. This is something that keeps much evil away from Muslims and helps them avoid committing many sins in the blessed month of Ramadan.
Also, refer to Fatwa 83888 about the Jinn sometimes appearing in a human form.
As for the little kid you mentioned in your question, we have no decisive answer about that matter.
Allaah Knows best.