So yeah, you can talk with other instances.
And if you want to migrate you should be able to download am your stuff and migrate follower lists etc
And if you want to migrate you should be able to download am your stuff and migrate follower lists etc
People are actively working on it to ensure that people can move across instances smoothly, but it's not yet there.
Y@J can announce they're moving and say where they're going, but there's no automated process. Several have been proposed, all (so far) can be horrendously abused. So far, X@I has to see the notification and follow Y@K manually.