Some are out of date, I think. I used the "define:" one so often that it became muscle memory for me. I was saddened when it stopped working a couple months ago. It'll still sometimes give you the word definition card, but I think only when just typing the word would give you the same card. I switched to typing "$word dictionary" instead, as I found it to trigger the definition card in almost every case where "define:$word" no longer would.
Of course, this relies on what data Google has on hand. Many of the examples provided in the article work because Google has so much data about "Apple" searches. The more niche the search operator, the more likely no results will surface. That being said, I've always found the "site:", "inurl:", and "+" or "-" operators to be incredibly useful for research reasons.
Define is broken in other fun ways. Try "define:inception". It won't tell you anything about the word, but everything about the movie unless you put it in quotes. But if you use something that's not, coincidentally, a movie title it works just fine.
