1. What is the difference between while and whilst?
2. When is it grammatically correct to use "the" with human being?
1. Both mean the same thing. "Whilst" may seem more formal to some speakers.
2. You would very seldom use "the" with "human being". An alien life-form in a piece of fiction might use it, to distinguish between two life-forms:
— "The human being appears to be a biped; but the dog is evidently quadrupedal."
Not a professional ESL teacher.