Explanation
The Stage Setup Flow is a tool that allows administrators to customize stages for leads and opportunities based on best practices from Salesforce experts. The Stage Setup Flow guides administrators through a series of questions about their sales process and then creates or updates stages for leads or opportunities accordingly.
The Stage Setup Flow also provides tips and resources for each stage such as key fields, guidance for success, reports and dashboards, etc. References:
https://help.salesforce.com/s/articleView?id=sf.stages_setup_flow_overview.htm&type=5

Explanation
Grant access using Hierarchies is a setting that can be used to configure the custom object to meet this requirement. Grant access using Hierarchies determines whether access to records of the custom object is granted through the role hierarchy. If this setting is unchecked, managers are unable to see the feedback records from their staff, unless they are given access by other means, such as sharing rules or manual sharing.
References:
https://help.salesforce.com/s/articleView?id=sf.security_sharing_owd_custom_objects.htm&type=5

Explanation
A sales process is a set of stages that an opportunity goes through as it moves from creation to close. It can be customized by administrators to match different business models or product lines within an org. Creating a new sales process can help Dreamhouse Realty define a different set of stages for its new home concierge offering that is unlike anything the company has offered in the past and follows a different business model.
Creating a quick action, a new approval process, or a new opportunity product are not solutions for creating a customized sales process; they are used for different purposes such as creating records, approving records, or adding products to opportunities. References:
https://help.salesforce.com/s/articleView?id=sf.customize_salesprocess.htm&type=5