Depends on how you’re accessing lemmy. There’s a button on lemmy websites if your instance’s admin has allowed it.

Don’t think so, easier to request someone on the other instance to create it for you.

To have loved and to be loved.

Just guessing, you might be the first person to try to visit that community/magazine from your instance, so lemmy doesn’t have the posts from before trying to federate.

There should probably be a message after federating a new community that tells people that old posts aren’t retroactively added to your local instance (unless done manually or unless that changes in the future). Or just something that tells users when a community was federated locally.

I think so. I haven’t needed to use it yet myself. I think it should forget the community and not federate future posts, unless some rediscovers/adds the community again. This is likely wrong sorry. An ability to block and purge specific remote instance communities seems pretty important.

As an admin, you can use the web UI to purge a community from your instance.