How to enable previous button in sub step(first sub step) /how to invisible/rename FPM buttons

Hi All,

1. I couldn't able to get a way to make enable the previous button for the first sub step , so I couldn't able come back to main steps until I finish my substeps..please find the screen shot for better view.
2. Second one -  how can I invisible the FPM stranded buttons(Previous/Next) and rename them.
3. Is there any way that I can trigger the FPM event(OVERRIDE_EVENT_GAF/PROCESS_EVENT) from web dynpro events ?

Thanks in advance

Rajesh