Questions regarding ultras, anarchists, trotskyists etc.

A couple of questions because I'm still uneducated on these things:

• Why do anarchists hate Marxists?
• Are anarchists and ultras the same thing?
• Are Trotskyists ultras and do they dislike Marxists?
• What are the differences between Trotskyists, Maoists and Hoxhaists? Are any of them comrades?