In Salesforce Revenue Cloud, when a new release is being deployed, it's important to test the implementation against the new release before it deploys to production. This can be achieved by:
Reviewing status.salesforce.com to determine refresh cutoff for the new release: Salesforce provides information about the refresh cutoff for the new release on status.salesforce.com. This allows you to know when the new release will be available in the sandbox for testing.
Determiningwhether your sandbox is on a preview or non-preview instance: Salesforce refreshes preview sandboxes a month before each major release. Regular, non-preview sandboxes are refreshed toward the end of the release cycle. Knowing whether your sandbox is on a preview or non-preview instance can help you plan your testing schedule accordingly.
It's worth noting that while Salesforce ensures that all sandboxes are upgraded, the timing of the upgrade can vary depending on whether the sandbox is on a preview or non-preview instance. Submitting a ticket to support when you want your sandbox updated is not a standard practice for preparing for a new release.
References
Test New Releases in a Sandbox Unit | Salesforce Trailhead
Salesforce Introduces Revenue Cloud to Help Businesses Accelerate ...

The three common CPQ design mistakes to avoid while implementing CPQ for your customer are:
A: Using price book entries to handle attribute based variations instead of lookup price rules: Price book entries are not designed to handle attribute-based variations. Instead, lookup price rules should be used. These rules allow you to adjust pricing based on specific product attributes, providing more flexibility and accuracy1.
C: Creating process builders and flows to pass data between fields instead of using twin field mapping:
Process builders and flows can be complex and difficult to maintain. Instead, twin field mapping should be used. This feature allows you to map fields between objects, ensuring data consistency and reducing the need for custom code1.
D: Writing customizations for product selection or validation instead of using option constraints, product rules, and bundles: Customizations can be time-consuming and costly to implement and maintain. Instead, Salesforce CPQ provides built-in features like option constraints, product rules, and bundles that can handle product selection and validation. These features are designed to enforce business rules and ensure that only valid product combinations are selected1.
References:
https://inspireplanner.com/blog/5-common-salesforce-cpq-implementation-challenges-and-how-to-avoid-them/

For the user story concerning sales users' ability to create new quotes with established rate cards and account- specific discounts, the Salesforce objects that need to absorb legacy datainclude:
B). Contracted Pricing: This object is crucial for managing special pricing agreements that have been negotiated with specific customers. It ensures that the pricing on new quotes reflects the discounts and rates that were originally negotiated under specific contracts.
D). Entitlements: The Entitlements object manages the customer's entitlements to support services or warranty conditions, which can be tied to the pricing or conditions stated in their original contracts.
These objects ensure that thecontractual terms and special conditions are respected in new transactions, maintaining consistency and honoring legacy agreements with customers.

Salesforce Revenue Cloud's CPQ (Configure, Price, Quote) solution allows for the creation of price rules that can be used to perform calculations on quote lines. In this scenario, the CPQ admin has created three separate price rules, each using a summary variable to add the net total for quote lines belonging to a particular product family. While this solution works, it may not be the most optimal from a performance standpoint.
Option D suggests using a single price rule with three price actions. This would be more efficient because it reduces the number of price rules that need to be evaluated. Each price rule evaluation can consume system resources and potentially slow down the quote calculation process. By consolidating the three price rules into a single one with multiple actions, the system only needs to evaluate one rule, which can improve performance.
It's important to note that summary variables in Salesforce CPQ allow you to perform a math function on the collected values of a number field on the quote line, product option, subscription, or asset1. You can also create filters so that the summary variable evaluates only fields on records that match the filter values1. This functionality would still be available with a single price rule with multiple actions.
References
* Summary Variable Fields - Salesforce
* Revenue Management Platform & CPQ Solution - Salesforce.com US
* Quote Line Groups - Salesforce