As we know, one of the simplest way to do a summation (with special intervals) over list elements is using

    Sum[list[[i]], {i, 3, 8, 2 }] (*with steps of 2*)

for a list such as `list={a, b, c, d, e, f, g, h, i, j, k, l}` which returns `c + e + g`.

How can we use `Replacelist` or `FoldList` to this aim?