Can you improve an IQ test score?

Yes, but... There is a common misperception that one's score on an IQ test infallibly tells how bright you are. Tests designed to measure one's intelligence rely on standardized administration of specific questions. If you've somehow been told the right answers in advance, you can score quite high on the test. That, sadly, does not mean your IQ is higher.
Depends. The IQ test is a measure of intellectual function.When preformed by a skilled observer it will generally produce results at a similar point level years apart.The individual being tested will never do better than they are capable, but can do worse, level of worry, sleep, nutrition, health may all hold someone back for one test, while they do better on another. I know of no way to inflate a score.