"Raghav is working with me since three years" is incorrect. The correct phrasing is "Raghav has been working with me for three years" because the present perfect continuous tense ("has been working") is needed to describe an action that started in the past and continues in the present. Also, "for" is the correct preposition to express the duration of time.
"Your behaviour is the best among all your friends" is also incorrect. The correct phrasing is "Your behaviour is the best of all your friends" because we use "of" when referring to the best or worst among a specific group.
Options B, C, and D are grammatically correct.