There isn't an easy way for us to discuss all of the ways in which people might use these general terms - that could be an entire chapter in a grammar book. It's also the case that, on this test, they never ask you to choose between different terms without giving you a specific sentence, and the details of that specific sentences are what allow us to choose the best answer. Finally, it's also the case that different terms can both (or all) be used correctly in a sentence; just because there's a difference does not indicate that one way is right and one way is wrong.
The best thing to do is to ask questions about specific problems. So, for example, go into those posts you've linked and ask, for example, what the differences are between using "unlike" and "in contrast to" specifically for the George Washington question. There are many circumstances in which a sentence can be correctly written using either of those terms. It just depends upon the construction and meaning of that specific sentence.
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Stacey Koprince
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