Explanation
The contact hierarchy is a feature that allows users to view contacts related to an account in a hierarchical tree structure based on their role or position within the account. The contact hierarchy respects record-level access by user, meaning that users can see only those contacts that they have access to based on their profile permissions and sharing settings. The other options are incorrect because contact hierarchy is not limited to
3,000 contacts at one time (it can display up to 5,000 contacts), customizing hierarchy columns does not change the recently viewed contacts list view (it only affects how contacts are displayed in the hierarchy), and sharing settings are not ignored by contacts displayed in the contact hierarchy (they determine which contacts are visible to users). References:
https://help.salesforce.com/s/articleView?id=sf.contacts_hierarchy.htm&type=5

Explanation
To capture the expiration date of warranty based on installation date and warranty length (1 year by default), the administrator should use a formula as the default value of Warranty Expiration Date field on Installation object. The formula can calculate one year from installation date using DATE function or DATEVALUE function. For example, DATE(YEAR(Installation_Date__c) + 1 , MONTH(Installation_Date__c) , DAY(Installation_Date__c)) will return one year from installation date. Creating a formula field, adding a validation rule, or including Warranty Expiration Date field on mobile page layout will not capture expiration date based on installation date and warranty length. References:
https://help.salesforce.com/s/articleView?id=sf.formula_using_date_datetime.htm&type=5