A clean way to handle 'cannot be said true or false' questions is to build two different worlds that both fit every clue, and see if a statement flips between them.
Statement I says a Belissima or Cassandra can never be an Elissima. This is not a matter of which world we pick, it is baked into the definition given for Elissima, 'neither Belissima nor Cassandra'. Every possible world must obey this, so I is always true, no world can break it.
Statement III says no one is Belissima, Alessandra, and Desdemona all at once. Since the clues already say no one is Alessandra and Desdemona together, adding 'and Belissima' on top only shrinks an already empty group, so it stays empty in every world. III is always true too.
Now try statement II, 'some Cassandras are Belissimas but not Alessandras', using two worlds:
Since both worlds obey every clue in the passage, but statement II flips between true and false across them, the passage simply does not fix its truth value. Statements I and III, by contrast, hold in both worlds because they follow directly from the definitions and the 'no Desdemona is Alessandra' clue.
Let's summarize:
So the statement that cannot be judged true or false is II only, option (2).
Statement: All flowers are beautiful. Some beautiful things are fragile.
Conclusion I: Some flowers are fragile.
Conclusion II: All beautiful things are flowers.