As the first wife, am I entitled to see my husband's polygyny application before the hearing?

Yes; a copy of the application and the husband's statement (iqrar) is usually served on each existing wife together with the court summons. The document states the husband's reasons, income, commitments and number of dependants. With it, you can prepare your response and evidence before the hearing date. Read it carefully and mark any inaccurate information, for example exaggerated income or undeclared debts. If you receive a summons without a copy of the application, ask at the counter of the Syariah Court that issued it. Keep all the documents safely. See evidence for the first wife.