Thanks for the explanation. I see now what you mean. I agree many (not all of them) SaaS apps need such tours but as far as I know, there is a ton of such apps. You can check some of them here, for example: https://userpilot.com/blog/best-user-onboarding-experience/
They create a specific layer that is put on top of your UI and guide users through it. But again, it requires a user to sign up at least.
We are creating something different. It's like an explanation video but users can participate in it. You will be able to create linear and non-linear scenarios to mimic a real product. It's not an explanation of the whole UI, but just what your product does, generally, what users can do with it.
well I mean... it depends. What problem are you trying to solve? The questions should revolve around that. You have the option of asking open ended questions as well as closed ended questions. but it's all down to the information you are trying to uncover.
Two sources I can recommend: Read the book Product Research Rules by CTodd Lombardo, and read this blog post: https://userpilot.com/blog/in-app-survey-questions-saas/