Mr. Spock, where art thou?

Is it rational to do something that you don't understand to achieve a purpose you don't want? I am studying for the LSAT. This is a bad move for many reasons. The first of which is that I don't want to really go to law school. The second is that I paid over a grand to take a test to go to law school. The third is that the test makes almost no sense. For example I memorized the following equivalent statements:

1. If X, then Y
2. If Not Y, then not X
3. All X are Y
4. Only Y are X
5. X only if Y
6. No X unless Y

Can someone please tell me how #4 works? You get a cookie. An imaginary cookie. Yum.

Formal mathematical logic (of which I'm comfortable with) is more like this:
~P=> Q
~Q=> P
Q U P
Q & P
Q P mind yours

Which is ok, and lets you solve a problem in math, rather than answering vague LSAT question stems or trying to logically arrange things for no apparent reason whatsoever.

The thing that bothers me the most is that I used to be so good at standardized tests. I could just rely on my good vocab and math skills. And though I'm usually good at logic and arguments, my fractured mind keeps knows an argument is wrong, but usually the reason it's wrong is not what Evil LSAT thinks.

So, of course, I must lower my resistance, and let the test show me what is wrong according to the test's own reasoning. But it's tremendously frustrating for me.

And then my mom yells at me that I need to change my life and study more seriously after I spend 3 hours, immobile, working on a logic game.

Sunshine is Sad.