How do colleges figure out if you are lying or not

Why would you even ask a question like that? I’ll take the high road and assume you’re concerned for a friend. Let your friend know things have a way of following you around in this world.

I work in the securities world. We are heavily regulated, thorough background checks, etc. Can cite many examples of people losing their registration with the SEC and FINRA (or their firm) several years after the fact when it was clear they had lied on applications (even for stupid things - Have you EVER been …). Careers and reputations get ruined. Tell your friend not to go down that path.