No, because the foundation is a compulsory subject, so whenever you take the exam, you can just pass it at last. If you choose one of the other four subjects, you can get a certificate after passing it, but the certificate after passing five subjects seems to be different from that after passing two subjects. So as long as you pass, it will be effective, but you must pass the second subject within two years after passing the first subject, which means you must pass two subjects within two years, so that your grades will be effective. Otherwise, only one subject will be passed within two years, and the result of the first subject will be invalid.