I'm not entirely sure which 'yanek' you specifically refer to. There could be many characters named Yanek in various works. More context is needed to accurately tell the back story.
The literary counterpart of flash fiction could be considered short stories. While flash fiction is extremely brief, often just a few hundred words or less, short stories are a bit more developed. They usually have a more complex plot, more fully - developed characters, and can range from a few pages to tens of pages. They share with flash fiction the ability to convey a complete idea or story in a relatively concise manner compared to a full - length novel.
It's hard to say. There are so many comics out there, and it depends on which comic universe or genre you're referring to. You might have to do some in-depth research.
I have no idea. Maybe it exists in some obscure comic series that I'm not familiar with. You could check with comic enthusiasts or search through specialized comic forums to get a clear answer.