Will these members self register with the sites or do you want them to enter the course anonymously?
1. If they are registered, then set up a self enrolment method for a newly created role (base it on student role). Give that role access to the first two sections only.
2. If they are not registered, set up guest access for the course and then hide sections 3-5 from guests. Set up feedback to be fully anonymous to allow them to complete it.