THEY CAN TAKE THEM OFF??? 😨😨😨

I hate this knowledge I've got SO many questions now that I never thought of and I KNOW no one can give me official answers 😭😭😭

Why can they take them off?
What are the benefits of having them on/off?
What are they made of?
When does a halovian get their halo?
What determines is shape?
Do they have feeling? Can you hurt a halovian's halo?
What is their actual purpose?
HOW IS IT STAYING IN PLACE?
Does the individual halovian get to decide where their halo is (sunday's and robins are at different spots on their heads), or is that predetermined by... whatever it is that predetermines the rest of this.
Can a halovian's halo change shape over time?
Does the halo get bigger over time?
Are halovians a long-life species?
WHY CAN THEY TAKE THEM OFF?