I can't see (4) ever being used in a correct answer on the GMAT in that form. Usually, if the subject and verb are reversed in a comparison, the meaning is different. It's not a straightforward comparison; instead, it means something like 'and the testmaker does the same thing.'
'Think, as does the testmaker' = the testmaker thinks, and you should think too. We could either think the same way, or differently, as long as we both think.
'Think as the testmaker does' = you should think in specifically the same way the testmaker thinks.
'I like to bake cookies, as does Laura' = Laura likes to bake cookies, and so do I. We could both bake cookies differently, or we could do it in the same way.
'I like to bake cookies as Laura does' = I like to bake cookies in exactly the same way (i.e. using the same ingredients, the same recipe, etc.) as Laura.