None of what you cited has anything to do with sustained practice.
IQ tests are generally accurate across a large population because very few people are practicing them, not because practice doesn't improve scores.
If you provided widespread incentive for people to practice IQ tests like colleges do for the SAT, they would cease to be an accurate measure of intelligence.
You admit IQ tests are generally accurate, and I showed that SAT scores are strongly correlated with IQ. Thus SAT scores are also generally accurate. So what’s your point?
IQ tests are generally accurate across a large population because very few people are practicing them, not because practice doesn't improve scores.
If you provided widespread incentive for people to practice IQ tests like colleges do for the SAT, they would cease to be an accurate measure of intelligence.