I’m deeply concerned about you with the same concern that God has. As your father, I promised you in marriage to one husband. I promised to present you as an innocent virgin to Christ himself. But I’m afraid that your minds might be seduced in the same way as the snake deceived Eve with his devious tricks. You might be unable to focus completely on a genuine and innocent commitment to Christ.
Paul here is in the middle of his diatribe against the false teachings of the “super apostles” that came to Corinth after he had left. Here he compares them to the serpent in the Garden of Eden who led astray Eve. The connection is clear: false teaching can twist the truth of the Gospel message and we would end up turning away from Jesus.
What is not so clear in today’s context is how we can tell whether something is a false teaching or not. There are so many different denominations and non-denominational churches in the world, how do we determine whether or not something is false? There are even some who would say that no one can make the claim that someone else’s belief is false if they hold that belief sincerely.
As for the last statement, that is blatantly false. The entire New Testament shows that there is a correct understanding of Jesus–Messiah and God in the Flesh–and there is a wrong understanding of Jesus–prophet who was killed and stayed dead. This is seen in the Gospels books. It is seen over and over again in the Church’s work in Acts, where some would not accept the truth and others would. It is seen in the letters, correcting false understandings. And it is seen in Revelation, where the main message is to hold on to the faith and not let anyone or anything turn you away.
As for how to determine whether the different denominations have truth or falsehood in them, the first thing to remember is that no denomination or faith fellowship will be perfect. This is not an excuse to put up with something you know in your gut is not right or true (see here). Having said that, one of the best ways to get at some obvious errors is to look at how the Church has understood a particular issue over the last 2000 years. With that much time on our side, and the guiding of the Holy Spirit to help us, chances are if something is a relatively new belief (250 years old or less), there is a good chance it is false. This is not a blanket statement, but a good guideline.
Beyond this, the only thing that will help in making this kind of decision is prayer and study. Find someone who is knowledgeable, has a strong faith, and is someone you trust, and talk to her or him about this issue. Together you will probably find the answer you need, because after all, Jesus promised to be wherever two or three are gathered in his Name.