What is the code of ethics and citation in course development
This depends on your definition of a "course". Is it an online course? Do you earn money with it or is it available for free? Or do you actually mean an old-school course taught at a school somewhere to a small group of people?

If it is a free online course, you should at least mention somewhere where you got some of your ideas from, as a courtesy to the other authors. The course they made might be part of their portfolio with which they apply for jobs, if your course then raises doubts concerning the originality of their work because you did not reference them properly, that would be bad. (You should also double-check whether they have written something about this topic somewhere, maybe they released their course under a Creative Commons license, for example.)

If it is an online course that you earn money with (Udemy or some other e-learning portal comes to mind), the situation is probably more complicated and there would be some legal issues that I don't know anything about. In this case you probably have to mention your sources and also ask for permission.

Finally, if it is simply a course taught in a classroom, I think it does not really matter. Your students will not care where you got your ideas for the design of the course from as long as the course is good and helps them to understand the topic.