The best feature to use to ensure consistent case priority entry is Path. Path allows users to see key fields and guidance for each stage of a process, such as a case lifecycle. Path can also enforce data quality by making certain fields required at each stage. See [this article] for more information on Path.

A roll-up summary field is a field that calculates values from related records. A roll-up summary field can be used to display the number of opportunities that are closed won with a close date within the last year on the account detail page by using a filter criteria on the field.

Formulas cannot reference child records, only parent records. This is a limitation of formulas that could be causing the issue. To include data from related child records, the app builder could use roll-up summary fields or Apex triggers instead

For managers to respond to approval requests for opportunities above $50,000 in the Salesforce mobile app:
B . In-App Notification: Managers receive notifications within the Salesforce mobile app when there is an approval request, allowing them to approve or reject directly from the notification.
C . Record Detail: Managers can access the approval request directly from the Opportunity's detail page in the mobile app, where they can review and respond to the request.
Steps to configure approval process notifications:
Navigate to Setup → Approval Processes → select the relevant approval process.
Ensure the process is active and configured to send notifications to approvers.
Managers need to have the Salesforce mobile app configured to receive notifications.
For best practices on managing approvals in Salesforce, see Approvals in Salesforce.

C: Setting the component visibility based on an advanced filter type, using the contact field(s) to define dynamic criteria, allows displaying information relevant to specific account conditions without needing user interaction.
Reference:
Salesforce Help - Dynamic Forms