Supporting inbound messages in each country would require additional long code implementation for MobileConnect. A long code is a standard phone number that can send and receive SMS messages. Each country has its own regulations and requirements for long codes, so a single long code cannot be used for all markets. The other functionalities do not tie to additional long code implementation. Reference: https://help.salesforce.com/s/articleView?id=sf.mc_moc_long_codes.htm&type=5