Each time a test is started, the number of questions at that time will be included in that test being taken. If you edit the test being taken, additional questions you might add will not be included. But if a new test taker starts the same test, they’ll get the new questions.
Editing the text of a question, such as fixing a typo, will permanently change the text for future, current and all past tests taken.
Editing how a question is scored will impact only future and current tests. Past tests taken will not be impacted.