It depends on the specific fanfiction. Some might depict Ash starting his serious training weeks before Hoenn, while others could have it just a few days in advance.
Well, in many fanfictions, Ash's training before going to Johto can vary greatly depending on the author's imagination. Sometimes it's intense and focused, while other times it's more laid-back and includes unexpected adventures.
Ash could develop his character in Sinnoh by becoming more strategic in his battles. Since Sinnoh has a variety of strong and unique Pokemon, he'd need to think more carefully. Misty could develop by becoming more independent. Maybe she takes on some solo adventures in Sinnoh, away from Ash for a bit, and this helps her grow as a trainer.
His first Sinnoh Pokémon could be a Chimchar. Imagine Ash finding Chimchar being bullied by some other Pokémon. Ash steps in and Chimchar decides to join him. Chimchar's energetic and mischievous nature would add a lot of fun to Ash's Sinnoh adventures as it grows and evolves into an Infernape.
It could be about a revised or remade version of Ash's adventures in the Sinnoh region in a fan - created story. Maybe it features new storylines, character developments, or different interpretations of the original Sinnoh plot with Ash as the central character.
There's also 'Ash and May in the Sinnoh Wilderness'. This fanfiction focuses on their exploration of the Sinnoh wilderness. They face various challenges together, like dealing with rare and powerful Pokémon. The way the writer describes their bond strengthening as they overcome these difficulties is really engaging. It also has some great descriptions of the Sinnoh landscape.
I'm not sure who the author is. There are so many fanfiction writers out there, and without more information, it's difficult to determine the specific author.
It could be about many things. Maybe it's a reimagined version of Ash's adventures in the Sinnoh region. It might feature new characters, new plot twists, or different interpretations of the original story.
Ash may develop his skills further in Sinnoh fanfictions. He could become more strategic in battles, learning from the different types of Pokémon and trainers in Sinnoh. May, on the other hand, might expand her knowledge of Pokémon contests, incorporating Sinnoh - style elements into her performances. Their experiences in Sinnoh help them grow both individually and as friends.