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Even after my analysis of my wrong questions, I am still not able to “have that instinct” to immediately see what the real question is.
You actually need to train yourself, consciously, how to do this. It's not an instinct.
For example, afterwards, when you figure out that you should have done XYZ, you then need to ask yourself, "What are the clues in the original problem that lead me to the XYZ approach / path / strategy? How should someone know that XYZ is a good approach here?
Look for explanations that explain not just WHAT to do but WHY to do it. (We try to do this in our own explanations. The official explanations for OG don't do this very well.) If you are discussing something with someone online, make sure to ask them WHY they did something, not just HOW they did it. "How did you know to think about that approach in the first place?"
As you do that, start to keep a file or make flash cards that use the "When I see... I'll think / do..." approach.
For instance, here's an easy one you already know:
When I see: +
I'll think / do: addition
And a somewhat more advanced one:
When I see: xy < 0
I'll think / do: x and y have opposite signs
And a very "test-taking" type one:
When I see: > 0 or < 0
I'll think / do: what does this problem have to do with positive and negative?
And an even more advanced one:
When I see: x + y > 0
I'll think / do: at least one of the variables must be positive (because two negative numbers can't add up to a positive number)
Once upon a time, you had no idea that + meant "add." You learned it in school and memorized it. The second one is probably something you learned in school, too, though you might have forgotten it until you started studying for the GMAT.
The third and fourth ones are much more specific to a test like the GMAT. The first time I saw that last one on a GMAT problem, I had no idea what the significance was, either. I asked myself: what are the kinds of numbers that would make this true vs. false? Both positive? Yes, that would work. One positive and one negative? That would work as long as the positive one is bigger in magnitude (farther from 0) than the negative number. Both negative? Ah! No, that won't work.
Then, I memorized that analysis so that I would just know the next time I saw something like that. (The reverse works, too: if x + y < 0, then at least one of the numbers has to be negative.)
At first, it might take you a long time on each question to figure that kind of stuff out. You'll be googling a lot to read what other people have to say about how they figured it out. (Again, not just how to do it, but how to know to take a certain approach.) As you start to get better and learn more about the GMAT "language," you'll become more efficient.
Don't think of it as a "killer instinct" to figure anything out from scratch the very first time you see it. I can't do that, either. I'm just trying to make connections to clues that I've seen before, so that I can think about things or follow the same path that I did when I saw a similar clue in the past.