Explanation
Splits is a feature that should be used to meet this requirement. Splits allows users to assign credit to opportunity team members based on the level of effort contributed by each person toward each deal. Users can create different types of splits, such as revenue or overlay splits, and specify the percentage or amount of credit for each team member. References:
https://help.salesforce.com/s/articleView?id=sf.forecasts3_splits_overview.htm&type=5

Explanation
To track shoe designs by products, prevent them from being deleted, and allow multiple designs for one product across various stages, the administrator should create a custom object for shoe designs and configure a custom lookup field for shoe designs on the Product object. This will create a one-to-many relationship between products and shoe designs, and allow users to link multiple shoedesigns to one product record. To prevent shoe designs from being deleted, the administrator can use validation rules or permissions. Adding a custom master-detail field for shoe designs on the Product object will create a many-to-one relationship, whichis not desired. Using the standard object for designs or configuring a validation rule will not meet the requirement.
References:https://help.salesforce.com/s/articleView?id=sf.customize_object_relationships_overview.htm&type=

Explanation
Standard objects are objects that are included with Salesforce by default, such as Account, Contact, Lead, Opportunity, etc. They have predefined fields and functionality that support common business processes.
Custom objects are objects that you create to store information that is specific to your organization or industry.
You can create new standard objects using the Object Manager in Setup. References:
https://trailhead.salesforce.com/en/content/learn/modules/data_modeling/standard_and_custom_objects

Explanation
Permission sets are used to grant additional permissions and access settings to individual users without changing their profiles or requiring a new profile to be created. You can use permission sets to extend users' functional access without changing their existing profiles. To meet the request of giving comprehensive edit access on Campaigns to a few marketing users who have read-only access by default, you need to create a permission set with edit access on Campaigns and assign it to those users.
References:https://help.salesforce.com/s/articleView?id=sf.perm_sets_overview.htm&type=5