Is there an official apple page explaining the age rating system for ios app development?
For example, specifically what qualifies as 4+, 9+, 17+ etc...
I saw online an image of a page where you can select radio buttons but I am not finding it on the developer website or an official definition of what is 4+ 9+ etc.
You are looking for App Store Help App Ratings:
Rating Definition
4+ Apps in this category contain no objectionable material.
9+ Apps in this category may contain instances of the following content that may not be suitable for children under the age of 9:
- Infrequent or mild cartoon or fantasy violence
- Infrequent or mild profanity or crude humor
- Infrequent or mild mature, suggestive, or horror or fear themed
12+ Apps in this category may contain instances of the following content that may not be suitable for children under the age of 12:
- Infrequent or mild medical or treatment-focused content
- Infrequent or mild references to alcohol, tobacco, or drug use
Simulated gambling
- Infrequent or mild sexual content or nudity
- Frequent or intense profanity or crude humor
- Frequent or intense horror or fear themed content
- Frequent or intense cartoon or fantasy violence
- Infrequent or mild occurrences of realistic violence
17+ Apps in this category may contain instances of the following content that may not be suitable for children under the age of 17:
- Unrestricted web access, such as with an embedded browser
Gambling or contests
- Frequent or intense mature or suggestive content
- Frequent or intense medical or treatment-focused content
- Frequent or intense references to alcohol, tobacco, or drug use
- Frequent or intense sexual content or nudity
- Frequent or intense realistic violence