What specific section and part of this act brought about the mentioned changes?
The changes mentioned are:

4. Ins. by the Constitution (Forty-ninth Amendment) Act, 1984, s. 4 (w.e.f. 1-4-1985).

5. Ins. by the State of Mizoram Act, 1986 (34 of 1986), s. 39 (w.e.f. 20-2-1987).

6. Ins. by the North-Eastern Areas (Reorganisation) Act, 1971 (81 of 1971), s. 71(i) and Eighth Sch., for "the Legislative Assembly of Assam" (w.e.f. 21-1-1972).

7. Paragraph 18 omitted by s. 71(i) and Eighth Sch., ibid. (w.e.f. 21-1-1972).

These changes were brought about by the following sections and parts of the respective acts:

1. Constitution (Forty-ninth Amendment) Act, 1984 - Section 4 (effective from April 1, 1985)

2. State of Mizoram Act, 1986 - Section 39 (effective from February 20, 1987)

3. North-Eastern Areas (Reorganisation) Act, 1971 - Section 71(i) and Eighth Schedule (effective from January 21, 1972)