When did these changes come into effect?
The changes mentioned in the given context were introduced at various points in time. Here's a breakdown of when each change came into effect:

1. Omitted by the Constitution (Sixty-third Amendment) Act, 1989, s. 3 (w.e.f. 6-1-1990). - This refers to an omission made in 1989 that came into effect on January 6, 1990.

2. Added by the Constitution (Forty-second Amendment) Act, 1976, s. 53 (w.e.f. 3-1-1977). - This change was introduced in 1976 and came into effect on January 3, 1977.

3. Ins. by the Constitution (Forty-fourth Amendment) Act, 1978, s. 40 (w.e.f. 20-6-1979). - This change was made in 1978 and came into effect on June 20, 1979.

4. Ins. by the Constitution (Fifty-ninth Amendment) Act, 1988, s. 3 (w.e.f. 30-3-1988) and ceased to operate on the expiry of a period of two years from the commencement of that Act, i.e. 30th day of March, 1988. (w.e.f. 20-6-1979). - This change was introduced in 1988 and ceased to operate on March 30, 1988.