For supporting attachments up to 25 MB and handling under 2,500 inquiries per day via free-form email, On-Demand Email-to-Case is the recommended solution. On-Demand Email-to-Case processes emails and attachments without requiring an email server, and is suitable for the specified volume and attachment size requirements, ensuring efficient case creation from customer emails.

To enable support managers to provide real-time feedback to agents during customer chat sessions, configuring Omni-Channel Supervisor is advised. This feature allows supervisors to monitor active chat sessions, providing an opportunity to offer immediate guidance and feedback to agents, enhancing the quality of customer interactions.

To provide contact center agents with access to a customer's payment history from an external billing system, configuring Salesforce Connect to integrate External Objects is advised. This solution enables real-time access to billing data directly within Salesforce, eliminating the need for direct access to the external system and streamlining the process for agents handling billing-related inquiries.

When additional requirements are discovered that impact the project's timeline and budget, preparing a change order to account for these requirements is the first step. This involves adjusting the project scope, timeline, and budget to accommodate the new requirements, ensuring that all stakeholders are aligned and informed about the changes and implications for the project's delivery.