Regarding their interview questions, you either know it or you don't. From my personal experience, Google's rounds of questioning are intentionally designed to weed out the people who fake it or try to cram up beforehand. For software engineering, they are interested in applicants who naturally demonstrate keen skill when it comes to CS fundamentals (algorithms, data structures, discrete mathematics, etc.).
Throughout my phone interviews, Marissa Mayer's quote "A good student excels in all subjects" kept running through my head. After interviewing with them, I believe Google holds all their employees to a similar standard.