You could probably find some ways to get a few of em but i don't know.
You shouldn't really need more than one or two accounts tho. Talking from kbin :)
One possibility is an instance shutting down. Many instance admins are good about giving lots of notice, but sometimes that doesn't happen.
In fact there has been at least one instance on the fediverse which the admin disappeared from the internet, and their instance just slowly degenerated until it stopped working. Were they hit bt a bus? Who knows.
In my experience, yes. I can see BeeHaw's content event though they defederated from my home instance a couple of days ago. I've also commented on some of their posts, which is weird...
If say, someone in Beehaw wanted to interact with Lemmy.World, they’d have to make an account on Lemmy.World or some other instance that hasn’t defederated