Well, generally in a Naruto fanfiction, the 20 parts might be divided in such a way. First, there could be the part that sets the time period, whether it's during the original Naruto series or after. Then, the part about the main character's new abilities or challenges. Also, parts for introducing new villains or allies. There might be sections dedicated to exploring different ninja villages and their cultures. And of course, parts for the big battles and how the characters grow from them.
One part could be about the Chunin Exams in great detail, showing all the exciting battles and the political intrigue behind it. Another part could be about the origin of the ninja clans in the Naruto world. Some parts might be dedicated to the daily lives of the villagers in the Hidden Leaf, which would give a more rounded view of the world. There could also be parts about how Naruto influences those around him, bringing out the best in his friends and comrades.
Sure, it can be normal. Just like any person might be interested in what others write about them or their alter - ego. It's a way to connect with the fan community on a different level.
Well, it could be a way for the daredevil to see how others perceive their character. Maybe they find it interesting to see the different scenarios and relationships that fans come up with in the fanfiction.
You could start with Naruto's childhood and his early days in the ninja academy for the first few parts. Then gradually move on to his first missions as a genin.
The Ice King's attempts to capture princesses always made for interesting parts. His complex character, being both a bit of a villain but also a sympathetic figure at times, was really engaging. Also, the episodes that explored Finn's past and his search for his true identity were quite memorable.