Questions on ABAP Dataflow

Hi Please answer my below queries on ABAP dataflow.

1. When using ABAP Dataflow with RFC data transfer, do we still need to use Data Transport and provide .DAT file name. I believe No .dat files are written in RFC Data transfer mode?
2. When we select Data Transfer Method to “RFC”, I believe “Working directory on SAP server” is not required. We can leave it blank. Right?
3. If we use Normal Data Flow for extracting data from SAP on “RFC Data Transfer Method”, Abap programs are still created and data is transferred over RFC         streaming or none of these applies to Normal DF?
4. Apart from SAP tables and Hierarchies can we use function modules inside Abap dataflow ?

Thanks in advance ,

     David king J.