Explanation
A roll-up summary field is a type of field that calculates values from related records, such as the count of child records or the sum of a field on child records. In this case, the administrator can add a roll-up summary field to the open house object to track the number of visitors by counting the child records on the visitors object.
References:
https://help.salesforce.com/s/articleView?id=sf.fields_about_roll_up_summary_fields.htm&type=5

Explanation
Case escalation rules are a way to automatically escalate cases that meet certain criteria, such as being open for more than a specified time or having a certain priority. Escalation rules can assign cases to a different owner or queue and send email notifications to the support manager or other recipients. References:
https://help.salesforce.com/s/articleView?id=sf.case_escalation.htm&type=5

Explanation
To identify new leads entered by interns from existing leads, the administrator should define a record type and assign it to the interns. This will allow them to select a different record type when creating leads, and distinguish them from other leads based on record type. Setting up Web-to-Lead form will not work if the interns are entering leads manually in Salesforce. Creating a separate Lead Lightning App or updating the active Lead Assignment Rules will not affect lead identification. References:
https://help.salesforce.com/s/articleView?id=sf.customize_recordtype.htm&type=5

Explanation
To acknowledge cases with a Case Reason of Installation immediately via email and assign them to appropriate agents, and escalate cases that are still in New status after 4 hours to support management, an administrator should use Auto-response rules, Queues, and Escalation Rules for case management.
Auto-response rules allow sending automatic email responses to customers based on case criteria. Queues allow grouping cases that share common characteristics and assigning them to a group of users who can access and work on them. Escalation rules allow escalating cases that meet certain criteria to higher-level users or groups and sending email notifications. Macros and Entitlements are not case management tools that can be used for this requirement. References:
https://help.salesforce.com/s/articleView?id=sf.case_autoresponse.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.queues_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.case_escalation.htm&type=5

Explanation
Case escalation rules are used to escalate cases that have not been resolved within a certain time frame by changing the case owner, sending email notifications, or triggering workflow actions. You can use these actions to alert the appropriate users or groups when a case needs urgent attention or escalation. References:
https://help.salesforce.com/s/articleView?id=sf.customize_caseesc.htm&type=5