Sentence A — "Everything is purposeless." — This is a philosophical opinion and cannot be objectively verified, hence a Judgement (J).
Sentence B — "Nothing before and after the existence of the universe is known with certainty." — This is a claim about the limits of human knowledge; though debatable, it is presented as a verifiable reality, so it is treated as a Fact (F).
Sentence C — "Man is a part of the purposeless universe; hence man is also purposeless." — This is a conclusion drawn from the premise in A, making it an Inference (I).
Sentence D — "There is only one way of adding purpose to this universe: Union with Him." — This is a recommendation or belief-based opinion, making it a Judgement (J).
Thus, the classification is: J (A), F (B), I (C), J (D) → JFIJ.