There is no single list of which I know.
A child account must be set up under Family Sharing. Until the child ages out of that, Family Sharing must be maintained.
There are some features a child can't account can't do such as allow app tracking. If an app asks to track your activity - Apple Support They also cannot change their birth date. According to the support article: Update the birth date associated with your Apple Account - Apple Support "If you need to change the birth date for someone below age 13 [age varies by country - see the article], contact Apple Support." There's others but I would have to spend 20 minutes looking through Apple's documentation. I believe some apps cannot be downloaded with a child account, even if the parent does not impose a restriction.
There are things that a child account does permit such as setting Ask To Buy but formally a child account is one for somebody under a particular age. Normally that is 13 but the age varies by country. However, once set, Ask to Buy will remain on an account until removed, so it is not exclusively for a "child account".