Show/Hide additional questions

What we want to achieve is this. We will be having a set of question groups all in two variants: "basic" and "expanded". For example SET1-basic consists of 2 questions and SET1-expanded consists of 5 questions (including those 2 from SET1-basic, so basically adding 3 more). Default view of the survey will be "basic" but I want to give an option to complete any group of questions also in "expanded" variant. The way I see this is that on the last question in each of the "basic" groups I will have some button saying "show extra questions". At this time a user can click "next" and go to next group of questions or click "show" and fill the extra questions. Of course a user can choose to complete all of the survey in "basic" options as well. Is this doable? Thanks!

Add multiple-choice question with a single sub-question to each group. Add relevance to the "expanded" questions so they are only shown if the corresponding checkbox is selected.