Please tell me the correct method for applying kojic cream on the face , whether it is necessary to wash it off after sometime and also whether it can be applied at night. Can it be applied on other body areas other than face. I mean will it be effective?

The cream you have should come with directions but it's probably as simple as wash your face and apply the cream, I'm sure it can be applied at night as well. I've seen kojic lotion before so I'm sure it's safe to use on the body.