Once the quiz is LIVE and you delete one of the answer choices or questions, you will lose all the response data for that question or choice. Keep in mind that you always have an option to download the report before deleting the choice. This way you can save the gathered data for version prior to your changes.
However, updating/editing questions or answer choice text won’t affect the data. Let’s say you published a quiz with the question “Which is the only breed of dog which can hunt both above and below ground?” Your answer choices are Terrier (10 people picked this answer), English Bulldog (5 answers) and Dachshund (4 answers.) If you later decide to change the last answer choice to “Weiner dog” instead of Dachshund, those initial 4 answers will remain and still be counted as correct.