You say that only C20 & C30 are added to the page as component presentations, and C1 is published as a dynamic component presentation.

This means that you will need to add some custom content delivery logic to your outputted page (or somewhere in your web application) to get that C1 component from the broker, and display it to the users. 

You state that C20 and C30 call rendercomponentpresentation for C1, but what gets rendered exaclty ? Could you post some sample output of your published page ?

There are some samples on how to work with dynamic component presentations in the tridion documentation on http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL%20Tridion%20full%20documentation-v1/GUID-7EC91BB9-707C-493D-8AA2-7E6414A307A8 (login needed).

Some more samples can be found on this page http://stackoverflow.com/questions/12799509/how-to-include-dynamic-component-presentation-in-the-tridion-page or here https://tridion.stackexchange.com/questions/3197/get-dynamic-component-presentations-on-the-content-delivery-side-using-the-api.



To answer your second question, something like this can be achieved by creating a custom resolver - some code samples can be found as well here : http://www.tridiondeveloper.com/the-story-of-sdl-tridion-2011-custom-resolver-and-the-allowwriteoperationsintemplates-attribute or here : http://www.tridiondeveloper.com/a-custom-resolver-in-practice