The Evangelion manga is typically regarded as canon. It expands on and adds details to the overall narrative, while remaining consistent with the core concepts and characters of the franchise.
The Evangelion manga is considered canon to a large extent. It offers additional details and perspectives that enhance the overall narrative of the Evangelion universe. However, there might be some minor differences from the anime that don't significantly impact the core storylines.
No way. Canonical content in Neon Genesis Evangelion is what was produced by the official studio and creators. Fanfictions, no matter how interesting or popular, are not part of the official lore. 'Lemon' fanfictions, which usually deal with more adult - like or unorthodox relationships between the characters, are completely fan - created and not recognized as official in any way. They are a form of fan creativity, but they have no bearing on the official story of the Evangelion series.
The story behind Canon in D is that it was composed in the Baroque period and has endured through the ages for its enchanting and repetitive melody. It's been used in many settings, from weddings to classical music concerts.
In general, the Evangelion mangas are considered good. They expand on the anime's universe, providing more depth and character development. However, it depends on personal preferences as some might find the style or pacing not to their liking.