Hard to say. Different manga have different characters. It's possible they're in some, but you'd have to do some research to find out exactly which ones.
Generally, manga don't have fillers. They tend to stick closely to the main plot and story progression without adding unnecessary content.
No, fictional characters don't typically appear on American Idol. It's a reality show based on real people's singing talents.
Yes, they do kiss at a certain point in the manga.
Definitely not. The manga portrays Ciel and Sebastian's interaction as professional and duty-bound rather than romantic, so there are no kisses between them.
Sometimes they do. It depends on various factors like promotions or special events.
Yes, they do kiss at a certain point in the manga.
Sometimes they do. It depends on the publisher's decisions and marketing strategies.
Sometimes they do. Publishers might update the box sets with new covers or additional bonus content.
Yes, they do. Many manga feature characters facing communication challenges as part of their story arcs.
No, 9/11 didn't feature directly in DC Comics.