Well, in the world of fanfiction, just about any concept can be explored, so it's highly likely that there is a 'harry potter is loki reincarnated' fanfiction. Writers love to mash up different universes and characters. This particular concept could bring in elements of Loki's mischievous nature into Harry's character, creating a whole new set of adventures and challenges for him in the Hogwarts setting.
Well, perhaps Loki, reborn as Harry Potter, would use his knowledge of other realms to bring in new magical concepts. For example, he might introduce Asgardian rune magic to the Hogwarts curriculum, which could cause a stir among the professors and students alike. He could also use his wits to outsmart Voldemort in ways that Harry might not have originally thought of, like tricking him into believing false prophecies.
Loki is a powerful Asgardian with abilities that are more in the realm of the supernatural in a different way than Harry's magic. But Harry has a strong will and has faced some extremely tough opponents. In a fanfiction, if the writer decides to give Harry access to some of the most powerful and ancient magic in the wizarding world, he could be more powerful. For example, if he could use the magic that created the Hogwarts itself, he might be able to stop Loki quite effectively. Also, Harry has the support of his friends and the entire wizarding community behind him, which could give him an edge in power.
It's hard to say. Loki has a wide range of magical abilities from Asgard. He can shape - shift, create illusions, and has a certain level of telekinesis. However, Harry Potter has the power of love and friendship on his side, which has proven to be a very strong force in his world. Also, Harry is very skilled at defensive and offensive magic within the wizarding world. So it really depends on the situation.
Yes, there are likely to be some. Fanfiction is a vast world and many creative writers combine different fictional universes like Harry Potter and Norse mythology. You can try searching on popular fanfiction websites such as Archive of Our Own or Fanfiction.net.
One idea could be that Loki, being the mischievous character he is, finds his way into the wizarding world of Harry Potter. He could start causing chaos in Hogwarts, perhaps by disguising himself as a student or a professor and playing pranks that are far more elaborate than those of the Weasley twins. For example, he might turn the entire Great Hall into an ice rink during breakfast time.
Loki's mischievous nature would definitely make Harry more of a prankster. Instead of just being the Boy Who Lived, he'd be the Boy Who Pranked. He might play tricks on Malfoy and his cronies more often and in more elaborate ways.
Loki's mischievous personality could make Harry more adventurous. Harry might start to take more risks in his magical studies and in facing Voldemort. For example, he could be more willing to try out untested spells or strategies.
One common theme is the clash of different magical systems. Since Loki comes from Norse mythology and Harry Potter has its own detailed magic system, seeing how these two interact is a big part of many fanfictions. For example, Loki's magic might be pitted against the spells of Hogwarts.
It could be a wild ride. Loki would bring his own brand of chaos to the wizarding world. He might start by using his illusions to mess with the Hogwarts students during exams, making them see their worst fears instead of the exam papers. His relationship with the professors would be complex. Some, like Snape, might be immediately suspicious of him, while others like McGonagall might try to keep him in line. And his interactions with the trio - Harry, Ron and Hermione - would be full of surprises. He could either be an ally or a foe, depending on his mood and his goals at the time.