Naruto: I Became the Strongest Ninja by Signing In

I can't understand it at the end

Book of Heaven, right? There is a new protagonist in one chapter. In the first chapter, the protagonist's name was Mu, but later he changed his name. This is still the first few chapters. In the previous chapter, it was clear that Kakashi took over the mission, but in the next chapter, it was Hayate leading the team again. Hayate Kakashi, right?

I was rewarded with Sage Mode at the beginning of the game, and I learned it later. I used it when fighting Deidara and Scorpion, and I learned it again after more than 80 chapters.

What does it mean to use a kaleidoscope as a chuunin?

You already have three books of heaven