Explanation:

All the statements are correct.
First is correct. The Preamble to the Indian Constitution is based on the ‘Objectives Resolution’, drafted and moved by Pandit Nehru, and adopted by the Constituent Assembly.

Second is correct. In 1949, India declared the continuation of her full membership of the Commonwealth of Nations but this declaration is not mentioned anywhere in the constitution.

Third is correct. Democracy is of two types—direct and indirect. In direct democracy, the people exercise their supreme power directly as is the case in Switzerland. There are four devices of direct democracy, namely, Referendum, Initiative, Recall and Plebiscite.
In indirect democracy, on the other hand, the representatives elected by the people exercise the supreme power and thus carry on the government and make the laws. This type of democracy, also known as representative democracy, is of two kinds—parliamentary and presidential.
The Indian Constitution provides for representative parliamentary democracy under which the executive is responsible to the legislature for all its policies and actions.