There will guaranteed be youtube videos of people going solo through everything. That said, they'll be extremely optimized, using every cheese/trick in the book. It's not something you'll just casually go through. You would get completely stomped.
Probably yes, but those will be highly specialized builds with advanced tactical knowledge that requires advanced understanding of all the details and intricacies of the mechanics behind the game. Most people will not be able to pull that off on their own...much less if they go in blind and don't have much knowledge of D&D. And given the vast spectrum of choice and consequence it will be nearly impossible to follow online guides for this stuff because you may end up going through entirely different areas and fighting entirely different enemies. The solo playthroughs may also use various skill monkeys to bypass encounters through skill checks and if you go down a different story path you may not have those options.
