The most reliable method to ensure high-quality sound (without the background hiss or low bitrates of unofficial "track-only" downloads) is to use official sources:
The Ultimate Guide to Watching Kung Fu Hustle with Hindi Audio Stephen Chow’s 2004 masterpiece, Kung Fu Hustle kung fu hustle hindi audio track download better
Yes, but you will need to resync it. The audio track doesn’t care about video resolution—only runtime. Use MKVToolNix to mux the Hindi audio onto the high-quality video. The most reliable method to ensure high-quality sound