I highly doubt it's a widely popular fanfiction given its rather strange and specific premise. Most popular fanfictions tend to focus on more common themes like romance, adventure or the characters' growth.
I'm not sure specifically as it's a very specific and likely self - created fanfiction. It could potentially be about a scenario in a fictional universe where Harry experiences this form of discipline from Bill. However, without reading it, it's hard to say more.
It's possible. In the realm of fanfiction, the imagination knows no bounds. Writers might come up with such a scenario for various reasons, perhaps to explore a different side of the characters' relationships. But it's not a common or mainstream concept within the Harry Potter fanfiction community, as it goes against the typical character dynamics we expect from the series.
At first, it might be a bit awkward as they come from different generations in the wizarding world. But as they spend more time together, they start to understand each other's strengths and weaknesses. Harry admires Bill's knowledge of magic and his courage, while Bill is drawn to Harry's selfless nature.
They could be like brothers. Harry has a strong connection with the Weasley family already, and with Bill and Charlie, it could be a natural extension of that. They might look out for each other and support one another in any difficult situation.
Yes, there are some out there. You can start by looking on fanfiction websites like Archive of Our Own. Some writers might explore unique scenarios where Harry and Bill have a moment of closeness that involves a kiss, often with different plot twists and character developments.
They could help Harry by teaching him new spells. Bill might teach him some advanced defensive spells he learned as a curse - breaker. Charlie could show Harry some unique ways to use magic around magical creatures. Hermione would of course be there to ensure Harry studies hard and understands the theory behind the spells.
In a fanfiction scenario, perhaps Hermione has a research project and enlists the help of Bill, Charlie, and Harry. Bill could offer insights from his travels, Charlie might contribute with his expertise on dragons as it relates to the research, and Harry would be there for moral support and to offer his unique perspective as the Boy Who Lived. It could be a story of friendship and cooperation in the magical community.
One common theme is mentorship. Bill often takes on a mentor - like role for Harry, guiding him in different aspects of the wizarding world. Another theme is friendship. Despite their age difference, they form a strong bond. Also, adventure is a common theme as they often embark on various quests or face challenges together in the fanfiction.