@floyd @adfichter Apple has historically used 3 mechanisms for geofencing that I'm aware of:
countryd, a system daemon introduced some time ahead of the EU Digital Markets Act coming into effect. This takes in various sources of information (location data, country codes broadcast by WiFi access points and cellular towers, etc.) and gives you a best guess as to which country the device is actually currently in (and has been in for some past time frame).Sometimes they use just one, sometimes a combination of those. But there's a good amount of things that change solely based on your physical location. One example is apps installed from 3rd party EU App Stores, which stop working if you've been physically outside the EU for some time. Another example is the mandatory shutter sound for Japanese iPhones. I own a second-hand phone that was originally sold in Japan, and after a clean restore it makes a shutter sound on camera use, but after some time (I think 2 weeks) of operation outside of Japan, that behaviour stops.
As for age range APIs, Apple Developer documentation has this to say:
Based on the person’s response, the system returns their shared age range with a lowerBound and upperBound, or if they’re in a nonregulated region, the system can return AgeRangeService.Response.declinedSharing.
This heavily suggests that they won't force age verification on users in regions where the law does not mandate it. What exactly happens when you travel between regions with different laws on this remains to be seen.