Yes, it is. The story of the Winchester House involves real people and real circumstances. Sarah Winchester's actions and the existence of the house itself are factual, although some details might have been embellished over time.
Not entirely. While it may draw some inspiration from real-life situations, much of the plot and details have been fictionalized to create a more engaging cinematic experience.
Yes, it is based on a true story. The Winchester House has a reputation for being haunted. Sarah Winchester, the owner, continuously added onto the house in a rather strange and haphazard way, which some believe was due to her trying to confuse the spirits she thought were haunting her. There have been numerous reports of strange noises, apparitions, and other paranormal activities in the house over the years, which has led to its fame as a haunted location.