Part I of the Constitution of India

Part I—The Union and Its territories is a compilation of laws pertaining to the constitution of India as a country and the union of states that it is made of.
This part of the constitution contains the law in the following examples=establishment, renaming, merging or altering the borders of the states or union territories. It also physically defines the words union / central government / government of India, states, territory of India, territory of a state, union territories and acquired territories which are used frequently in the constitution. This part contains four articles. These articles were invoked when West Bengal was renamed, and for formation of relatively new states such as Jharkhand, Chhattisgarh, Sikkim, etc.
Articles 1 & 2.
 says that India, that is Bharat, shall be a union of states and the territory 
The acquired territories can be converted in to a state/states as per Article 2. Jammu and Kashmir get converted to Union territory in 2019. Ladakh was also so converted. 
Sikkim was a special case which was included as a completely new type of statehood under a new Article 2A and conditions mentioned in tenth schedule, and was called 'associate state'. But this experiment failed and Sikkim was later added to Indian Union by Constitutional Amendment Act (1975).
With the seventh amendment to the constitution in 1956, the concept of Union territory is brought in to administer areas which are very small in area or governed by international agreements or politically not evolved for locally elected governance. The representation of seats in the council of states (Rajya Sabha) shall be as given in Schedule 4 of the constitution. The territorial waters and the exclusive economic zones shall also become part of the territories of states or union territories in the absence of any listing of them separately in Schedule 1 and 4 of the constitution. There is no separate representation in parliament though people inhabit on these offshore areas for exploiting resources such as fisheries, oil and gas, etc.
The constitution (40th amendment) act, 1976, was passed during the emergency period and received Presidential assent on 27 May 1976. It amended the (earlier also amended by the constitution [15th amendment] act, 1963) so as to vest in Union of India all lands, minerals, and other things of value underlying the ocean within the territorial waters or continental shelf or exclusive economic zone of India.
The territorial waters, continental shelf, exclusive economic zone and other maritime zones act, 1976 was enacted by the Indian government to notify the sovereign rights on these areas for dealings with other countries. However, these maritime zones are also parts of the states as they are not separately listed in schedule 1 of the constitution and the role of union government is limited to mainly defending the offshore territory from external threats.
States are not debarred from imposing taxes or royalty on the minerals extracted from the territorial waters and the exclusive economic zone (which are under states jurisdiction) as per serial no. 50 of state list in seventh schedule (Taxes on mineral rights subject to any limitations imposed by
Parliament by law relating to mineral development) of the constitution.
Article 3.
Article 3 talks about Formation of new States and alteration of areas, boundaries or names of existing States: 
Article 3 says: Parliament may by law:
(a) form a new State by separation of territory from any State or by uniting two or more States or parts of States or by uniting any territory to a part of any State
(b) increase the area of any State;
(c) diminish the area of any State;
(d) alter the boundaries of any State;
(e) alter the name of any State;
Provided that no Bill for the purpose shall be introduced in either House of Parliament except on the recommendation of the President and unless, where the proposal contained in the Bill affects the area, boundaries or name of any of the States, the Bill has been referred by the President to the Legislature of that State for expressing its views thereon within such period as may be specified in the reference or within such further period as the President may allow and the period so specified or allowed has expired 
Explanation I: In this article, in clauses (a) to (e), State includes a Union territory, but in the proviso, State does not include a Union territory 
Explanation II: The power conferred on Parliament by clause (a) includes the power to form a new State or Union territory by uniting a part of any State or Union territory to any other State or Union territory
Article 4.
Article 4 is invoked when a law is enacted under Article 2 or 3 for the marginal, incidental and the consequential provisions needed for changing boundary of a state or union territory. As per , no such law framed under Article 4 (1), shall be deemed to be an amendment of the constitution for the purposes of article 368.
Before 1971, there were few articles [Articles 4 (2), 169 (3)-1962, 239A (2)-1962, 244A (4)-1969, para 7(2) of Schedule V and para 21(2) of Schedule VI] other than Article 368 which permitted marginal amendments to the constitution. However Article 4 (2) got superseded by the 24th amendment in the year 1971 to Article 368 (Power of Parliament to amend the Constitution and Procedure there for). was added by 24th amendment which says that notwithstanding anything in this Constitution, parliament may in exercise of its constituent power amend by way of addition, variation or repeal any provision of this Constitution in accordance with the procedure laid down in this article. Constituent power means eligibility to frame constitution and make amendments to the constitution. Supreme court observed that article 368 (1) clearly defined the scope of constituent power which is power to make amendments, variations or deletions to the constitution. Constituent power conferred on the parliament must be exercised by it in accordance with the procedure given in article 368 (2) and can not be subjected to an inferior legislative procedure under article 4 or delegated to an outside agency. Thus there is only one procedure for bringing an amendment (including of marginal nature) to the constitution which is the procedure given in Article 368. However, these superseded articles [Articles 4 (2), 169 (3), 239A (2), 244A (4), 356 (1)c, para 7(2) of Schedule V and para 21(2) of Schedule VI] have been in use for enacting laws for not contesting their validity in the court of law.
External links.
Supreme court verdict on Non-obstante clause