Hi Hellen,
Both these behavior are as per the design of intercompany solution:
1. When Global item is updated from the sender company then Item properties replicated by intercompany solution overwrite the item properties of the receiver company. The system is designed to keep the complete master data in sync and mirrored limited to the properties replicated by the Intercompany Solution.
2. The Intercompany document exchange flow is unidirectional and not bidirectional. A PO added in the Sender Company will create a draft SO in the receiver company not vice versa. This is well documented in the Intercompany User Guide.
Regards,
Agneesh Jain
SAP Intercompany Team