Oh Yes, very common problem
Yes. If not it will be a wet vent and cause MAJOR problems.
Yes, you can adjust the toilet clog to clause your toilet to overflow.
the water pipes of the 2 items are probably connected in the same pipeline. Poor venting or a stoppage down stream
Iron in the water would cause rusty stains in the toilet.
wrong stuff placed in the toilet
NO way
No.
No. It can only cause problems.
it is connected cause the birds use to sing
Bad parts
cause it just is
No one is really certain what causes autism but you can be fairly certain that dirty toilet seats do not.