I'm not sure exactly when it was released. You might want to check the official publisher's website or some reliable book news sources for the accurate date.
The back story of KH is quite complex and involves a series of events and characters. It all started with a mysterious incident that set the stage for everything that followed.
In the German original, Rapunzel is portrayed as a rather innocent and naïve girl. She has been locked in the tower for a long time, so she is somewhat sheltered. When the prince comes, she is easily charmed and falls in love quickly. Her long hair is not just a physical feature but also a symbol of her captivity and later, her connection to the outside world.
One possible fanfiction could be about Roxas and Xion exploring the new worlds in KH3 together. They might face new enemies and challenges while also reminiscing about their past. Their bond could grow stronger as they help each other through difficult situations.
In most cases, the KH light novels are considered canon. They often expand on the existing lore and characters in a way that fits within the established framework of the series.
Rapunzel is definitely not true. It belongs to the realm of fantasy and folklore. Tales like Rapunzel are often used to spark the imagination of children and adults alike, but they have no basis in reality.