Negan is indeed alive. The comic storyline has continued to develop his character and his interactions with other survivors have been a significant part of the plot.
Yes, it can be. It can serve as an introduction to Negan's character, which is a significant part of the 'Walking Dead' story. Even new fans can quickly get into the story and understand his role.
Well, Negan's defeat in the comic was a result of multiple factors. The main characters came up with a clever plan, and they also received unexpected help at crucial moments. Plus, the group's determination and teamwork played a big role.