Leukemia is a form of cancer that occurs in the blood cells. The bone marrow makes too many white blood cells, and sometimes these cells don't work right because they keep growing when they are supposed to stop, and grow faster than other cells. Over time, the cancer cells take up too much space, so there is no room for healthy white and red blood cells.
Presumably, yes. At the end of the movie, she is swinging on the swings when her cap flies off, revealing that her hair has all grown back. This means that the chemotherapy has ended. It is never explicitly stated that Janice is free of cancer, but that is the most likely circumstance.
Yes; there are no glaring factual errors. Janice's explanations about what tests were performed and her chemotherapy were accurate.
A number of organizations offer information about leukemia:
*The Leukemia and Lymphoma Society (http://www.leukemia.org)
*National Cancer Institute (http://www.cancer.gov)
*The American Cancer Socity (http://www.cancer.org)
