Good luck in the tests but don't worry if you don't get past the cubes... it's a cognitive skill that you either have or you don't... familiarity with the questions will make you more relaxed and allow your brain to work on it without the distraction from stress... it won't make you "better" at solving them because that just comes down to how your brain is hard-wired (the structure of your brain as it's developed from childhood and your genes).
...although, I did read an article last week about exercising your brain during your life... so maybe people can improve the structure and performance of their brain over time... a long time I suspect.