Good trick. I see it now, I'm assuming this only works for fischer projections?You need to translate those diagrams into 3D shape. It is a difficult transition, but I have a trick.
Consider the upper half and lower half of the molecule separately. If you look at A, C, D, you must switch 2 substituents on the lower half to get the same configuration as the upper half. For example in A, you must switch the location of Br and H, in C, Methyl and H, in D, Br and H. However in B, you must switch the location of all 3 substituents to get the same configuration as the upper half.
What this means is an useful trick in stereochem. If you have to switch 2 substituents of one molecule (or a part of molecule) to get the same looking as the other molecule (or the other part of the molecule), they're non-superimposable mirror images. If you have to switch 3 molecules, they're basically the same molecule with diff conformation. So if you rotate the lower half of B, the two parts will look the same, so there will be a mirror plane -> meso.
I can't answer your question about that trick, because I've never used it, but if you draw them out in a sawhorse you will also see that A/C/D are the same moleculeGood trick. I see it now, I'm assuming this only works for fischer projections?
Also, This would mean that if a, c, and d are non-superimposable they are also enantiomers correct?