i think he’s saying he can’t select the one in particular without all of them being selected.
i sometimes have problems myself when i select something and some other part of something else way off miles away and not included in within the selection area, gets selected also. but i think this may be some sort of virus i picked up somewhere somehow having invaded my instal of blender. except my example only happens when i have a really loaded up scene with tons of stuff in it.
at any rate two solutions, neither guaranteed, but what usually works for me, is to use those twenty layers. put things you don’t want selected together on different layers from each other, and select the one or ones you want, with only the layer you’ve put them on, turned on.
the other thing, even then, is whenever you, use circle select rather then box select. circle select seems to do a better job of only selecting what you intend with it. box select is quick to select stacked verticies in edit mode.
i have a personal standard of what kinds of things i put on what layers. cameras have their own layer, light sources have theirs, and then different kinds of geometry have theirs.