Yes, oddly enough, it's just called "hoarding." I don't know if there is a different term other than pathological hoarding.
ask them
No
YOU can't tell them. A mental health professional has to asses and diagnose them.
Mental illnesses are mostly genetic. If there are no genetic markers then the chances of someone experiencing a mental illness sometime in their lives is not likely. If symptoms are present a doctor should be contacted immediately.
The word psychological describes someone's mental or emotional state. This term is used when someone has a mental illness instead of a physical ailment.
No. That's called fantasy.
The term "mental illness" refers to someone who has a mental (brain) related deficiency. Some of these mental illnesses affect your mood, behavior or actions.
Assault causing bodily injury or mental illness involves intentionally causing harm to someone's body or mind, resulting in physical injuries or mental health issues.
Sinusitis is not caused by mental illness. Mental illness can be caused by sinusitis infection.
Mental illness predates recorded history.
not guilty by reason of mental illness
This is a tricky one, as it depends on the individual as well as what illness it is that they have. More information would be nice, if possible