Hi Kanthu,
Re: #1 - There are no special tools for debugging or testing. For the most part debugging is done using the Sourcing logs.
Re: #2 - I'm not sure I understand the question
Re: #3 - Together Workflow editor is used to develop approval workflow. We have recently (9.0 SP16 and above) added an in-application workflow editor which is a replacement for the Together editor.
If you are interested in learning more about SAP Sourcing configurations I'd suggest listening to the Sourcing webcasts on SCN. For scripting and workflow, you can look at the Scripting and Workflow guide available on SMP. If you want to attend a training, go to SAP Education website and search for TSO150. It's a 5 day technical training that covers configurations, scripting, workflow, etc.
Hope this helps.
Regards,
Vikram