It depends on your perspective. Some parts might be based on real events, but it's likely to have fictional elements added for dramatic effect.
Not entirely. Bugsy probably incorporates some real elements, but it's also likely that a lot of it is fabricated or exaggerated to make it more cinematic and entertaining.
Well, it's a bit of a mix. While it may draw inspiration from certain real-life circumstances, it's not a completely accurate account of actual events. The filmmakers likely took some liberties to make the story more engaging.