Explanation:

3rd statement is incorrect. The Cabinet Secretary is under the direct charge of the Prime Minister.  There is no fixed tenure, the average tenure of the Cabinet Secretary has been less than 3 years.
Functions:

• Cabinet Secretariat prepares the agenda of the meetings of the cabinet.
• The secretariat is to collect all necessary informations as to how the various ministries and departments have practically materialized the decisions taken in the cabinet meetings.
• It is the duty of the Cabinet Secretariat to keep the President of India, the Vice-President of India and all the ministries of the government well informed about the impor­tant activities and decisions of the government of India.
• It is his duty to give advices and discuss elaborately all problems of inter-departmental nature and on the matters related with the question of co-ordination among the different departments.
• On permission from the President of India and being directly ordered by the Prime Minister of India the Cabinet Secretariat finalizes the rules of business and distributes the works to be done among the different departments of the government of India.
• It is also the duty of the Cabinet Secretariat to provide with all types of secretariat assistance to the other various cabinet committees.