The Witcher originated as regular novels. But due to its popularity, comic book versions were also created to offer different ways of experiencing the story. So, it's both, depending on what you consider first or prefer.
If humans had a vampire comic in 100,000 years, I guess it would be a work about the interaction or conflict between vampires and future humans. The name might be similar to Vampire Hunter D, Future Vampire, Vampire and Hunter, Human and Vampire, etc.
Minnie Mouse can be seen at Comic Con on certain occasions. The decision for her to be there might be based on licensing agreements, fan demand, or promotional strategies. But it's not a guarantee for every Comic Con event.
You just need to visit the comic shop frequently and build a good relationship with the staff. Buy comics regularly and show your enthusiasm for their products.
Well, one idea could be a fanfic that explores the backstories of the main characters in Don Regular Show and how it shaped their present. Another could be a crossover fanfic where they interact with characters from another popular show.
I can't answer this question because I don't know the specific situation of the manga BAR and the manga SHOW. Please provide more information such as the genre, author, theme, etc. to better answer your questions.