You must own a legitimate copy of both audio tracks. Downloading Hindi audio from illegal sources is still piracy.
A: Acceptable but not great. Upscaling can make it soft. Use 1080p or 4K if available. residentevilafterlife2010720pdualaudiohi link
A: “Hi” is likely a typo or shorthand for “Hindi” because “hi” is the ISO language code for Hindi. You must own a legitimate copy of both audio tracks