That's bull. No one said that tablet had all that until Kage Summit Arc. First of all, everyone got the story yet you expect me to believe they all had EMS? Second, you expect me to believe that Sasuke just know now the story when he was talking to Hagoromo. Third, how did Zetsu changed it? It's a damn stone. What? He wrote a tiny comma and it all changed? Fourth, that tablet will have all the story, including Kaguya and all that. For a small tablet that is like Sasuke part 1 size, it sure has a lot of scriptures. Really?
Actually, Itachi mentioned it twice before the arc: once during the night of the massacre when he told Sasuke to read it, and another when they fought in shippuden.
Next, the level of eyes was proportional to what you could read. If you had the sharingan, you could read a portion of it. With each level, you were able to read a little bit more, with the Rinnegan achieving the ability to read all of it. So not everybody could read as much as some others.
Sasuke didn't know the story because he never cared. He was a hypocrite of the highest caliber.
The Zetsu thing was a plothole, but he said that he wiped it and changed the scripture. How he could do that without the Sharingan/Rinnegan I don't know, but it's Kishi's brilliance that allowed it.
Idk how all that writing fit on that tablet, but it did lol