1. I think it is just like the sql adapter – although the adapter probably turns the Xml input into something else. Did you check the sample included with the Oracle Adapter? I do not know if you can do a dynamic select though. The receive adapter wants something to be defined or to call a stored procedure.
2. No, I don’t think you need to use the pipeline concept.
3. I think you should just need add the aspnet to the BizTalk Application Users group. That user needs to have rights to write to the message box.