Webservies integration in HPSM 9.40

This is regarding webservies integration with HPSM
1.    I wanted to know where the fields can be made as mandatory or optional based on actions in the webservices configuration example as closure codes should be mandatory on close action, but need not to be mandatory on Add action. Where to map fields for each action? and where to how to make it mandatory? Was this needs to be modified in ScriptLibrary "IncidentManagement"
2.   How can I put some conditions and filter the incoming transactions when the requests come from 3rd party tool to HPSM. Where to do this? Expressions does only the calculations on a field. But how to filter the transactions based on the conditions in HPSM? Example: If the transactions has to move from 3rd party to HPSM only when assignment group is "xxxx", and other transactions should not pass.
3.   How to track the error/failed messages when transactions flow from 3rd party to HPSM? Are there any log files for tracking messages?
4.   For failed transactions, where to set the re-iterations for those failed transactions and how?
5.  Can the WSDL for each module be combined to make in a single WSDL(A common WSDL for all the operations related to each module?