In some fanfictions, Harry's disappearance could lead to the discovery of new magical powers or places. Maybe he stumbles upon a hidden magical realm while in hiding. This new place could have its own set of rules and powers. As he tries to figure out how to get back to Hogwarts or deal with the situation that made him disappear in the first place, he has to learn about these new powers and make alliances with the beings in this new realm.
Yes, there are some out there. You can start by looking on fanfiction websites like Archive of Our Own or FanFiction.net. Just search for 'Harry is a Runemaster before Hogwarts' in their search bars and you'll likely find several stories to choose from.
If there was a rivalry before Hogwarts, it could carry over and make their interactions at Hogwarts more tense. However, this could also lead to them pushing each other to be better. For example, in Quidditch, if Fleur is also a good flyer, Harry might strive to outperform her, which could improve his skills as a Seeker. And over time, this rivalry might turn into mutual respect.
The story would be drastically different. Without Harry, there's no Boy - Who - Lived to be the main antagonist to Voldemort. Hogwarts might not be the safe haven it was in the original series. Voldemort could target the school more directly, and the students would live in constant fear.
One reason could be that he's being hidden by some powerful magic from a group that wants to use him for dark purposes. Maybe there are dark wizards who know of his future importance and want to either kill or control him, so a good wizard has made him disappear.
Yes, there are quite a few. Some fanfictions explore Harry being trained by his parents' friends in secret before going to Hogwarts. For example, he might be taught basic magic skills like levitation or simple spells by Sirius Black or Remus Lupin. These fanfictions add an interesting twist to the original story, showing a more prepared Harry when he finally steps into Hogwarts.
Well, perhaps Harry inherits some rune - related knowledge from his parents. He unknowingly uses runes to keep himself safe from the Dursleys' worst behavior. When he finally goes to Hogwarts, he realizes that his rune knowledge is far more advanced than his peers. He might then use it to solve mysteries around the school, like decoding ancient runic inscriptions in the castle. He could also make friends with those interested in runes and together they form a sort of rune - study group that uncovers secrets about Hogwarts' past.
Clearly, it's Harry and Hermione. Harry, an orphan living with his cruel aunt and uncle, and Hermione, a muggle - born girl with an inquisitive mind. They are the focus of this fanfiction set before Hogwarts. Harry has his unruly hair and a sense of loneliness, while Hermione has her bushy hair and a passion for books. Their personalities start to develop even before they step foot in Hogwarts.
The setting in which Harry disappears and returns also matters. If it's in the middle of Hogwarts, the school would be in chaos. Teachers would be trying to keep the students calm while secretly searching for Harry. And when he returns, the reactions of different houses - Gryffindor being relieved and proud, Slytherin perhaps being suspicious - could add more layers to the story.
Maybe he meets an old Canadian witch who has a lot of wisdom about a certain type of magic that is rare in the UK. She could give Harry some valuable advice or a magical item that helps him later at Hogwarts.