Al-Jawab Billahi At-Taufeeq (the answer with Allah’s guidance)
1) No, this is not true.
2) Jinns are generally devious and deviant, and can cause much harm to humans. However, to learn the techniques and practices to control Jinn is permissible but should be left to those who possess knowledge of the art, and every person is not to venture in to this field.
3) They are called Jinns because they conceal themselves from people’s sight.
Allah Ta’ala says,
O Children of Adam! Let not Shaitan (Satan) deceive you, as he got your parents (Adam and Hawwa (Eve)) out of Paradise, stripping them of their raiments, to show them their private parts. Verily, he and Qabeeluhu (his soldiers from the jinns or his tribe) see you from where you cannot see them. Verily, We made the Shayatin (devils) Auliya (protectors and helpers) for those who believe not. (7:27)
The actual form of Jinns is fire.
“And the Jinns did He create from a smokeless flame of fire.”
And Only Allah Ta’ala Knows Best.
Moulana Qamruz Zaman