Reference:
https://docs.microsoft.com/en-us/powerapps/maker/model-driven-apps/optimize-form-performance

A: With advanced data preparation available in Power Apps, you can create a collection of data called a dataflow, which you can then use to connect with business data from various sources, clean the data, transform it, and then load it to Microsoft Dataverse or your organization's Azure Data Lake Gen2 storage account.
B: By combining conditions and actions, you can do any of the following with business rules:
Set column values
Clear column values
Set column requirement levels
Show or hide columns
Enable or disable columns
Validate data and show error messages
Create business recommendations based on business intelligence.
C: Duplicate detection works by comparing generated match codes of existing records with each new record being created. These match codes are created as each new record is created. Therefore, there is potential for one or more duplicate records to be created if they are processed at the exact same moment. In addition to detecting duplicates as they are created, you should schedule duplicate detection jobs to check for other potential duplicate records.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/data-platform-create-business-rule
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/create-and-use-dataflows
https://docs.microsoft.com/en-us/powerapps/developer/data-platform/duplicaterule-entities

Scenario:
Customers can select a meal when they make a reservation and can save the meal choices as a customer preference.
The company offers two types of meals: standard and vegetarian. Meal types can be temporarily unavailable. The airline is considering offering other meal types, such as gluten-free and low-sodium options.
In PowerApps Option set is one of the field types you can use in your Entity. The information type that Option Set stores is a list of text values. And here comes the Option Set advantage - once you define its text values you can centrally managed it.
Example:

Reference:
https://michalguzowski.pl/how-to-work-with-option-set-in-powerapps/
Topic 1, Relecloud
Current environment
The company uses Microsoft Office 365.
The company has a custom app for managing and tracking passenger luggage. The app uses Microsoft Dataverse.
For flights longer than four hours, passengers receive a meal. Customers can select a meal when they make a reservation and can save the meal choices as a customer preference.
The company offers two types of meals: standard and vegetarian. Meal types can be temporarily unavailable. The airline is considering offering other meal types, such as gluten-free and low-sodium options.
The company uses paper-based reservation checklists to help ensure that all the steps for a reservation are complete.
The company uses vendors to service aircraft.
Environment
Ensure that employees can sign in to all Microsoft apps by using one set of credentials per employee.
Minimize the use of third-party products and custom development.
Reduce customer support call volumes by having the system automatically resolve common issues.
The security rule for agents must contain the privileges in the default Customer Service Representative security role.
Log issues as cases. The case form must show variable sections based on the case type. Include a custom entity named Seats and grant agents access to the entity.
Application use layout should be role specific.
Agents
You must standardize the format used by agents to enter customer phone numbers.
Agents need a solution to replace paper reservation checklists.
Agents need dashboards to show a current count of all reservations on the entity.
Agents need a way to track reservation issues.
Agents need a visual indicator in the interface to determine the reservation step to provide a seamless customer experience.
Agents need different versions of cancellation policies to send customers. One version must be controllable within the system.
Agents need to view which pieces of luggage match to each passenger, and then need to add the total on the passenger record.
IT
IT staff needs a mobile solution to see IT cases at the top of the menu since this is their primary focus.
IT staff needs a system that is easy to navigate to active cases.
IT specialists want to design Power BI reports. They need to understand the underlying table relationships of the system.
IT specialists need a solution that is visual rather than text-based so they can quickly complete their tasks.
Management
Management requires paginated reports for stakeholders.
Management wants to provide frequent flyers with better service when the flyers call.
Managers need to see all customer dashboards at the top of their menu on their mobile device.
Maintenance
Maintenance supervisors must not have access to Dynamics 365 Customer Service. The supervisors must be able to communicate with the contracts team about contracts.
Aircraft maintenance vendors must have only view and upload privileges to their invoices and receipts.
Contracts with maintenance companies must be stored in Dynamics 365 Customer Service.

Reference:
https://docs.microsoft.com/en-us/power-platform/admin/wp-data-loss-prevention
https://docs.microsoft.com/en-us/power-platform/admin/control-user-access