My OnePlus 2 (latest official android was 6, it’s running lineageos android 11 though) also got its assistant swapped with Gemini so idk

It’s actually a whole list of requirements. https://grapheneos.org/faq#future-devices

I mean, not quite. There should be a split between backend (logic) and frontend (presentation) even for desktop applications. It’s not mandatory, but simply much better design. The ‘interface’ with which your frontend code calls the backend is much like an API (as in an API is also an interface)

In Europe that used to be the case, but that changed not that long ago. Now providers are legally obligated to allow you to get your own modem