Who takes over the office of President when there is a Vacancy by reasons of death, resignation, removal by impeachment or otherwise?

Chairman of Rajya Sabha

The correct answer is Option 1 - Chairman of Rajya Sabha

Chairman of Rajya Sabha is the Vice President of India.

When there is a vacancy in the office of the President of India due to reasons such as death, resignation, removal by impeachment, or otherwise, the Vice President of India takes over the office of the President until a new President is elected.