Nothing4You

instances get added automatically once they reach a threshold of monthly active users. iirc it’s >6 mau, you could check the code to confirm.

you can find your user info in the /api/v3/site response. the /api/v3/user endpoint requires a name or person id.

i recommend checking out https://join-lemmy.org/api/classes/LemmyHttp.html

you can only set a community to only allow local users, not prevent users from interacting with remote communities.

you’d have to either disable federation or set up a script to automatically remove all remote communities, but that also won’t be a per user thing, just a per instance thing.