What changes occurred to the number of reserved posts for members of a particular community in 2020, and how does this compare with previous periods?
In 2020, the number of posts reserved for members of a particular community in the services mentioned changed from "seventy years" to "sixty years." This change can be traced back to several amendments:

1. The Constitution (Forty-fifth Amendment) Act, 1980, s. 2 (w.e.f. 25-1-1980), changed the words "forty years" to "thirty years."
2. The Constitution (Sixty-second Amendment) Act, 1989, s. 2 (w.e.f. 20-12-1989), changed the words "thirty years" to "fifty years."
3. The Constitution (Seventy-ninth Amendment) Act, 1999, s. 2 (w.e.f. 25-1-2000), changed the words "fifty years" to "sixty years."
4. The Constitution (Ninety-fifth Amendment) Act, 2009, s.2 (w.e.f. 25-1-2010), changed the words "sixty years" to "seventy years."
5. The given context states that the words "seventy years" were substituted for "eighty years" by the Constitution (Eighty-second Amendment) Act, 2000, s. 2 (w.e.f. 8-9-2000).

Regarding the changes in the number of reserved posts during subsequent periods, the context provided states that during every succeeding period of two years, the number of posts reserved for members of the community shall be less by ten percent than those reserved during the immediately preceding period of two years. The reservations will cease after ten years from the commencement of the Constitution.