What are Interrogatories Propounded To Defendant-First Set in a child support/modification to shared parenting case?

Yes, you must answer the interrogatories. And, you can send him a set to answer too.

Interrogatories must be answered within 28 days of service in Ohio. You daughter's father is entitled to information from you to defend against the modification.

Based on this question, it seems you do not have counsel and he does. If he has counsel, then you need counsel because there are objections that can be raised to the questions and the attorney will use your answers to defeat your claim at modification. If you have an attorney they will assist you in responding.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.