It depends on your perspective. Some might consider it new as it brings in new elements and developments. But in a broader sense, it still builds on the existing Scott Pilgrim universe.
Definitely. 'Scott Pilgrim Takes Off' draws inspiration directly from the comic. It retains many of the key elements and storylines from the source material.
Scott Pilgrim is likely to be one of the main characters. He has been central to the previous stories. Ramona Flowers is also probably a main character as she has a major role in Scott's life.