Two functions that an administrator should use when creating a validation rule are:
Error condition formula, which defines when an error should occur based on record fields and values Error message location, which specifies where on the page layout an error message should appear when triggered by an error condition formula Formula return type and rule active date are not functions used for validation rules. Reference: https://help.salesforce.com/s/articleView?id=sf.validation_rules_overview.htm&type=5

Manual sharing allows record owners to share individual records with other users or groups. This is useful when one-off sharing is needed for a specific situation. Hierarchical sharing, criteria-based sharing and owner-based sharing are not suitable for this scenario because they are based on predefined rules or roles that do not match the requirement. Reference: https://help.salesforce.com/s/articleView?id=sf.sharing_overview.htm&type=5

To display the screen flow, the administrator should create a tab and add the screen flow to the page. The administrator can also use a flow element and add the screen flow to the record page.
The other options are not relevant to this scenario. Adding the flow in the utility bar of the console will not display the screen flow. Installing an app from the AppExchange is not necessary to display the screen flow.
Here are the steps on how to create a tab and add the screen flow to the page:
Go to Setup > Tabs.
Click New.
Enter a name and label for the tab.
Select the Screen Flow tab type.
Select the screen flow that you want to display.
Click Save.
Here are the steps on how to use a flow element and add the screen flow to the record page:
Go to Setup > Customize > Lightning App Builder.
Select the record page that you want to add the screen flow to.
Click Edit.
Drag the Flow element from the Palette to the canvas.
Select the screen flow that you want to display.
Click Save.

A validation rule is a tool that allows administrators to enforce data quality and integrity by preventing users from saving records that do not meet certain criteria or conditions. For example, a validation rule can display an error message if a user enters an invalid value in a field. In this case, the administrator can create a validation rule on the account object that displays an error if the account annual revenue field is below 0 or greater than 100 billion. Reference: https://help.salesforce.com/s/articleView?id=sf.validation_rules.htm&type=5

Dynamic dashboards allow you to display data according to the security settings of the running user. If users have different access levels to data on dashboards, you can use dynamic dashboards to show them only what they are allowed to see.