So if you’ve published a game, just keep on keeping on. You can sell that game, maintain an older copy of Unity to update it for bugs, even develop new content for that game with the older version of Unity.

According to the article, probably no.

Many devs may have updated unity and used it for minor updates, but also the clause in question probably doesn’t protect anyone anyway. There’s a broader ToS that supercedes it with much more restrictive language.