It's hard to say for sure. The availability of Venti in the story depends on multiple factors such as the story's genre, setting, and the author's intentions. It could be possible, but you'd have to look closely at the story's details to know for sure.
Well, in a Venti identity reveal fanfic, it could involve Venti dropping his carefree bard facade and showing his more divine or ancient side. It might include scenes where he has to use his true powers to protect Mondstadt from a great threat. And this could lead to a whole new understanding of his character by the people of Mondstadt and the readers of the fanfic.
Well, without reading it specifically, it could be about Naruto in a scenario where he becomes the champion in a context related to Raiden. Maybe it involves Naruto facing challenges in a Raiden - inspired world or having to prove himself worthy of some sort of Raiden - related title. It could also potentially involve Naruto using powers or abilities associated with Raiden.
The length of the Raiden Shogun story quest can be quite subjective. On average, it might take around 3 to 5 hours. However, if you take your time to enjoy the cutscenes and dialogue fully, it could extend longer.
The OC could be designed with a strong sense of justice, just like Raiden. For example, if the OC is a human, they could be a warrior who has always fought for the rights of the oppressed. This would align them well with Raiden's mission to protect Earthrealm. Their moral compass would be in sync, which would make their interactions more believable and natural.
Well, Naruto is surely one of the main characters since it's in the title. As for others, it could include characters from the Naruto universe like Sasuke, Sakura, Kakashi, etc. depending on how the story is set up. And there might be new characters introduced that are related to this Raiden concept, perhaps a Raiden - like figure who is an important part of the plot.
Dark Raiden's story is quite complex. He started as Raiden, the protector of Earthrealm. However, after seeing so much violence and the constant threat to Earthrealm, he became darker. He decided to take more extreme measures to protect his realm. He was tired of the rules that seemed to be constantly exploited by the enemies. This led him to make some very controversial decisions, which put him at odds with some of his former allies.