Well, 'Rumbling Hearts Visual Novel' stands out for its music and sound effects too. The background music sets the perfect atmosphere for each scene. The sound effects, like the gentle rain when a sad scene is on or the bustling noise in a crowded place, add to the realism and immersion of the game.
I'm not entirely sure as I haven't read it in detail. But generally, a visual novel often involves a story with characters, plot twists, and multiple endings. 'Rumbling Heart' might be about relationships, emotions, or personal growth of the characters in the story.
It's a bit hard to give an exact number. Different regions might have different releases and editions. You could look into official Kingdom Hearts sources or fan communities for a comprehensive list.
The Kingdom Hearts manga is indeed canon. It's been approved and integrated into the overall Kingdom Hearts narrative. While it might present some events or details differently from the games, it still contributes significantly to the broader story.
In general, Kingdom Hearts doesn't strictly adhere to the manga. The game has its own unique plot and gameplay elements that set it apart. Some characters and events might be inspired by the manga, but there are substantial deviations.