File-XI-multiple IDoc Scenario

Hi there -

I am working on single File-XI-multiple IDoc Scenario and have following questions:

(please keep in mind that there is already an existing multiple IDocs-XI-single File scenario between the same systems)

1. Please provide any detailed step by step documentation from end-to-end.

2. I am thinking it's compulsory to use BPM, is there any way to aviod?

3. Is it possible to update existing IDocs in R/3 directly from the data from XI?

Thanks everyone in advance...

Pat