The jinn may appear in human or animal form; they may appear in the form of snakes, scorpions and so on; or in the form of camels, cattle, sheep, horses, mules and donkeys; or in the form of birds. They may also appear in human form, as the devil came to Quraysh in the form of Suraqah ibn Malik ibn Ja`sham, when they wanted to go out to Badr.

There is nothing wrong with you killing snakes that are outside the house. As for those that are found inside the house, they should not be killed until they have been warned for three days.

When Allah commanded the angels to prostrate to Adam, He included Iblis in that because, even though he was not one of them, he was imitating them and doing deeds like theirs.

Seeing the angels and the jinn, in a form other than their true form, is possible. As for suggesting that only children can see that, we do not know of any text which speaks of that. This is a matter of the unseen, and we cannot say anything about it except on the basis of evidence, and there is no evidence to deny or affirm that.

If someone reads the messages that contain fortune-telling and predictions for the future believing in them, then he is rightfully subject to the warning which says that he has disbelieved in what was revealed to Muhammad (peace and blessings be upon him) and that no prayer will be accepted from him for forty days. For more, please see the detailed answer.