If you mistakenly selected "Yes" when it should have been "No" in the JEE Advanced registration form regarding a child of a deceased or permanently disabled defense personnel, you should contact the JEE Advanced authorities immediately to rectify the error. They may provide a correction window or allow you to update your details through a specific process.

Here's what you can do:

1. Contact the JEE Advanced Helpdesk:

Reach out to the official JEE Advanced helpline by phone or email to explain the situation and request guidance.

2. Check for a Correction Window:

Some years, JEE Advanced provides a correction window to allow candidates to rectify errors in their application forms. Look for any announcements or updates on the official website regarding a correction window.

3. Follow the JEE Advanced Instructions:

If a correction window is not available, follow the specific instructions provided by the JEE Advanced authorities on how to address the error. This might involve submitting a separate form or providing additional documentation.

4. Seek Clarification:

Ask the exam conducting authority about the specific documents they require and whether any alternatives are acceptable.

5. Provide Correct Information:

If you have the opportunity to rectify the mistake, ensure you have all the necessary documentation ready and follow the provided instructions.

Important Note: Misrepresenting your category or eligibility can have serious consequences during the admission process, so it's crucial to address the mistake as soon as possible.