compiling questions

A few quick compiling questions about compiling:

In the Project Customizer, what all is listed in the Compiler combo box? 
Internal Compilation + all registered Java Platforms?

Is there still going to be a Platform tab in the Customizer? How will 
the user register new platforms? Basically I'm just wondering how you'd 
choose to compile something with a different compiler executable.

When you build a single file, does it also build any dependent files 
that are out-of-date?

Thanks,

-John