Quick answers
Can you rebind the controls in Castlevania: Belmont's Curse?
Yes. Settings › Controls has a Controller tab and a Keyboard and Mouse tab, and every action can be moved. If two actions end up on the same button, the game marks them “Already assigned”.
What are the keyboard controls for Belmont's Curse?
The game has a full Keyboard and Mouse tab and Steam lists a keyboard-only option, but no source this page can check shows its default keys yet, so none are listed here. Steam marks the game Gamepad Recommended.
How do you backflip in Belmont's Curse?
Press Dodge while standing still — Circle on PlayStation, B on Xbox — and Rose dodges backwards. Press it again during that dodge and she goes even further back.