1KA allows you to make immediate changes to the questionnaire, but you need to be careful if the survey is already active and in the data collection phase. You can easily add new categories and change the text of old ones, but if you remove a category, the data in the database will also be removed.
If the survey is not yet active, then you can change the question type very easily. If you have selected the wrong question type, e.g. 'Categories - Single answer', but would like to use 'Categories - Multiple answers' or any other question type instead, simply click on the question toolbar and the question settings will open. In the 'Basic' tab of the question settings, you will see the 'Question type' dropdown, from where you can select your desired question type and the existing question will automatically be restructured accordingly.