The President of India is the supreme head of state of the Republic of India. The President is also the Supreme Commander of the Indian Armed Forces. The President of India can exercise the executive power of the Union of India either directly or through subordinate officers. The President can also pass ordinances, which have the same force and effect as an act of Parliament. 

The President can also dissolve the Lok Sabha, the lower house of Parliament, on the advice of the Prime Minister. The President can also declare a state of emergency in the country, if he is satisfied that the security of India or any part thereof is threatened by war or external aggression or by internal disturbance. 

The President of India is elected by an electoral college consisting of the Members of Parliament and the Members of the Legislative Assemblies of the States and the Union Territories. The President is elected for a term of five years and can hold office for a maximum of two terms.

Yes, a president's ordinance can amend the Indian constitution. This was established in the case of Madan Mohan Malaviya v. The Province of Uttar Pradesh, AIR 1946 PC 98. In this case, the president's ordinance was upheld as valid and constitutional.

The President of India is the supreme executive authority of the Government of India. The President's ordinance-making powers are derived from article 123 of the Indian Constitution. Article 123 empowers the President to promulgate ordinances when both Houses of Parliament are not in session. The President must ensure that the ordinance is approved by both Houses within six weeks from the reassembly of Parliament. The President's ordinance-making power is subject to judicial review. The president must be satisfied that there is a need for such an Ordinance.

In the case of Lakshmi Kant Pandey v. Union of India, the Supreme Court held that the President's ordinance-making power is not absolute and is subject to the basic structure of the Constitution. The President's ordinance-making power has been used to amend the Indian Constitution. In the case of S.R. Bommai v. Union of India, the President's ordinance-making power was used to amend the Constitution to provide for the President's rule in the states.

The president's ordinance-making power is subject to certain restrictions. 

Firstly, the president can only make an Ordinance when both Houses of Parliament are not in session. 

Secondly, the president must be satisfied that there is a need for such an Ordinance.

The president's ordinance-making power is an important constitutional power. It enables the president to take immediate action in case of an emergency. It is, however, subject to certain restrictions.