Explanation
A sales agreement is a record that captures the terms and conditions of a long-term or run-rate business relationship between a manufacturer and a customer. It can include products, product categories, prices, volumes, schedules, and other details. A sales agreement can have a maximum of 1500 products or product categories and 72 schedules. Contact Salesforce support if you want to increase the limits. Note that having a large number of product or product categories and schedules can affect system performance1. References: Considerations for Working with Manufacturing

Explanation
According to the Salesforce Manufacturing Cloud documentation, to apply a rebate program to more than one account, you need to add each account to the members related list on the rebate program. This way, you can enroll multiple accounts as members of the same rebate program and track their transactions and payouts. You can add one account at a time, or use an existing Accounts list view to enroll multiple members. You can also enroll an account in multiple rebate programs if needed1. References: 1: Enroll Members to a Rebate Program

: Program Based Business is a feature of Manufacturing Cloud that allows manufacturers to track and manage the demand from their end customers (such as phone brands) and compare it with the actual orders from their channel partners (such as distributors or contract manufacturers). This feature helps manufacturers to plan for future opportunities, optimize their inventory and production, and increase their market share. Program Based Business enables manufacturers to:
Create programs that represent the end customer demand for a specific product or product family over a period of time.
Associate sales agreements and orders with programs to track the actual performance against the program demand.
Use program analytics to monitor the program health, identify gaps and risks, and take corrective actions.
Use program forecasts to generate account forecasts based on the program demand and actuals. Reference: Program Based Business Overview, Create a Program, Associate Sales Agreements and Orders with Programs, Use Program Analytics, Use Program Forecasts.