I used examples from an actual Stanford-Binet IQ test. They did indeed want to know the odd one out from apples, corn, carrots, and a couple of other vegetables. And it’s not entirely out of the question that they’re after basic taxonomic groupings, because the same test had kangaroo as the odd one out (requiring you to know about marsupials).

Anyway, that the Flynn effect has stopped in industrialized countries (but probably not in, say, Kenya…it showed huge gains from ~1980 to ~2000 when most industrialized countries were plateuing) does not negate its utility in judging that there are massive environmental effects. And I’m not sure what point you’re making with different tests giving the same results — of course, otherwise g wouldn’t really be a measurable thing. This says nothing about what determines it.

As far as cursive goes — well, maybe, but I think any manner of similar thing ought to give the same practice (piano, engraving, decorative icing of cakes, etc.). Given the lack of success in any other relatively brief intervention, the safe bet is to bet against it, but it’s hard to know without doing a study.