In this fanfiction, Naruto might go back to the time when he was a child. He could use his future skills and wisdom to outwit his enemies from that time, like Orochimaru. He could also help his friends, like Sasuke, in a different way. Maybe he could prevent Sasuke from leaving the village in the first place. This would lead to a completely different story arc for both of them and for the whole Konoha village.
Obviously Naruto himself. Since he is the one going to the past, he would be the central character. His younger self would also be important as he would interact with his future self.
He would probably use his leadership skills. Naruto has grown into a great leader as Hokage. In the past, he could quickly assess situations and lead others, whether it's in a battle or in village - building activities.
Well, it depends on the specific fanfiction. Some fanfictions might explore alternate storylines where Naruto doesn't become the Hokage at all. Maybe he decides to pursue a different path in life, like focusing on being a teacher or an explorer. However, in a large number of fanfictions, he does achieve his goal of becoming the Hokage because it's such an iconic and desired outcome for fans who want to see his journey to the top in different ways.
He could change a lot of things. Maybe he would prevent some tragedies that happened in the original story. For example, he might be able to save some characters who died. He could also use his knowledge from the future to make the ninja world a better place earlier, like teaching new jutsu to the younger versions of his friends.
It could be the First Hokage, Hashirama. Naruto would be amazed by his powerful Wood - Style jutsu and his ability to create the village. He could learn about the original ideals behind the Hidden Leaf from Hashirama.
A recurring theme is redemption. Maybe a past Hokage had made some mistakes in their time and now, through Naruto, they get a chance to make things right. Also, the exploration of the political situations during the time of the past Hokage is common. How they dealt with other villages and internal conflicts.
His friends like Sakura and Shikamaru would surely support him. Sakura, with her medical skills, could be an important part of his regime, providing healthcare for the ninjas. Shikamaru, being intelligent, could offer strategic advice. Also, the younger generation of ninjas who have been inspired by Naruto would be his strong supporters, as they believe in his leadership and the new direction he could take the village in.
Sasuke could be an alternative. He has strong ninja skills and a deep understanding of the ninja world. His experiences have made him grow into a very capable person, and his Sharingan gives him an edge in combat and strategic planning.
There's also 'Naruto: Uncovering the Past Hokage's Mysteries'. This fanfic focuses on Naruto's journey to discover hidden secrets about the past Hokage. He uncovers things like their unfulfilled dreams and how they can be achieved in the present day, which gives a fresh perspective on the Naruto universe.