I get what you're saying, but you also wouldn't say it was discovered in 1966 as it was simply theorized without any direct evidence. A lot of things are theorized before they are actually discovered to exist.
That's what discovery is: realizing that something exists and describing it.
You're talking about creating, using, verifying, observing, etc. There are lots of things Einstein discovered that we are still verifying. It doesn't mean he didn't "discover" general relativity.
Not quite. If I understood correctly, Nagaoka predicted magnetism in a thin material with electron deficiency. This happened in a thin material with 50% excess of electrons, which arguably is different or at least something Nagaoka didn't exactly predict.
The best part is it was just copied from another site, at least it was cited. I sent to the site and it said the article is based on an article from another source.