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?

I am learning important functions (FoldList and ReplaceList) which are used instead of (Accumulation) in sum over list, in which I faced to some problems and could not find correct things. Instead of accumulation, for a simple summation what does it work!?