I've been studying demonology and exorcism for about 30 years.
Demons can and do kill children.
Demons can possess anyone who allows them to get a foothold in their life, the process is not quick, but they tend to be persistent.
The only way to remove demons from a possessed person is through an exorcism.
A "minor rite" exorcism usually involves only one priest, an assistant, and the possessed person, and is usually performed in the possessed persons home.
They use the Roman Rite of Exorcism, usually only a few sessions provide deliverance.
A "major rite" exorcism is called for when major devils are involved or in those instances where the demons involved are particularly violent.
This can involve several priests, a number of assistants, the possessed person and medical staff to handle any injuries that may occur.
These are usually performed in a Church related hospital.
Normally none of this is filmed and any information is kept private (mainly to avoid the idiots and sensationalism that often follows).
For the most part only Catholics, Orthodox, and Lutherans perform exorcisms.
A inquest is ALWAYS performed before the exorcism to determine if a demon is really involved (versus insanity).
People who have not been formally trained in exorcism should not attempt to perform one, the demons have no issues with murdering idiots and the foolhardy.