SAP EWM Inbound Reversal / GR Reversal / ERP IBD Deletion

Dear Colleagues,

        Can some one tell me the process of reversal of the Inbound Documents in landscape ERP and EWM where.

1. In EWM putaway and GR are completed. ( I See that the only way to reverse is to create a return order )

2. Putaway done but no GR done ( Reverse the putaway and reject the IBD but the IBD in ERP does not gets updated.

3. No putaway or PGR done  ( Reject the document in IBD but we cannot reject IBN ( notiication ) and hence the ERP docuemnt still shows distributed.

Can some one tell me the right process for different scenarios above to update both EWM and ERP.

Thanks

Sandeep kumar