Support for Opera wasn’t a completely separate effort, it just happens to work because, like you said, it’s Chromium based. If it wasn’t, it wouldn’t be supported either…
It's a way to share your contact information with other iPhones. Similar to AirDrop but you can setup what gets shared and how their phone saves your contact info.
You're the first I've heard doing this, how does the interior screen work with Graphene? Are there any optimizations to take advantage of it? Or limitations (split screen apps?)? Sorry if these are dumb questions
Not sure if you saw, but Mozilla announced desktop extensions coming to mobile soon too.