multiple of your questions are already answered by the Mendix introduction course.
My advice is to take the course and first get familiar with how to develop with Mendix.
You can find the course here: https://gettingstarted.mendixcloud.com/index3.html
this particular one can be found in the module: "Advancing the User Experience", in the chapter Smart Pages.
Set conditional visibility of the div based on value of radio button.