depending on the anime and depending on the age of the kid. some animes aren't made from children, just because it's cartoon/anime dooesn't mean it's all for kids. there are many animes such as full moon wo sagashite, shugo chara and prince of tennis which is fine for children. they were made to target a younger age group.
fantastic children. :)))
High School of the Dead. Period. It is borderline Hentai.
dirty
I do not not exactly by what you mean by dirty anime, but I will try my best in answering your question. For really eechi and percerted anime, try this: Kanokon, KissxSis, School Days. For really messed up Anime, try: School Days (really messed up), Wlecome to the N.H.K. (Not that messed up). For a really gory, sad but romantic anime, try: Elfen Lied
Yes, most of them do. Anime if popular among children and teens.
hamtaro is a good anime for little children
Reddit, 4Chan, or even google (possibly)
Probably
Yes.
because its dirty?..
no, just innapropriate
It's a popular running gag usually referencing the nosebleeding person has seen or thought dirty things.