Questions about jury duty

Going off of another post, I just have some questions about it. I'm in Canada btw.

1) How severe can the cases get when being called for jury duty?

2) Do they pick adults at random, or do you have to sign up for it?

3) Do they choose people with a mental illness like anxiety and depression?

4) Is it true that only one person has to say the suspect is innocent for it to be ruled as not guilty? Or does it go by the majority?

5) Can you say no to being on jury duty or do you HAVE to do it?

I'm just wanting to know because I would really not want to be on jury duty and I have bad anxiety and depression and I know in court they go into gross details about the crime and I know I couldnt handle it.