There are quite a few out there. 'Bella and Kate: The Lost Years' could be an interesting read. It might delve into a period of time that was lost in their lives and how they rediscover themselves during that time. Some fanfics also focus on their growth as individuals within their friendship, like 'Bella and Kate: Growing Pains' which shows how they deal with the difficulties in their relationship while also growing as people.
Sure. One popular Bella and Kate fanfic could be 'Bella and Kate's Adventure'. It often features their unique friendship and the various challenges they face together in a fictional world. Another one might be 'Bella and Kate: A New Beginning' which could explore their new experiences in a different setting.