When an administrator deletes a custom field, Salesforce moves it to the deleted fields list for 15 days, during which time it can be undeleted or erased permanently. If the administrator undeletes the field within 15 days, most of its properties and data are restored, except for its field history data, which remains deleted and cannot be recovered. References: https://help.salesforce.com/s/articleView?id=sf.custom_field_delete.htm&type=5

A user with manager role above the agent can change ownership on multiple cases that are owned by the agent or by users below the agent in the role hierarchy. A user with the System Administrator profile can change ownership on any case, regardless of the owner or role hierarchy. References:
https://help.salesforce.com/s/articleView?id=sf.case_change_owner.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.admin_userperms.htm&type=5

Flow builder is an automation tool that allows administrators to create flows that guide users through screens, collect data, and perform actions on records. It can be used to simplify the account creation process by creating a screen flow that shows only the essential fields for creating an account and hides any unnecessary fields or sections from the page layout. Approval process, workflow rule, and validation rule are not automation tools that can simplify the account creation process; they are used for different purposes such as approving records, updating fields, or enforcing data quality. References:
https://help.salesforce.com/s/articleView?id=sf.flow_builder.htm&type=5

Compact layouts determine which fields appear in the highlights panel on record pages and in the Salesforce mobile app. To create a custom compact layout, go to the Account object manager and select Compact Layouts from the sidebar menu. Then click New and add the desired fields to the layout. References:
https://help.salesforce.com/s/articleView?id=sf.compact_layouts_create.htm&type=5

Record types allow you to update the options in a picklist based on the kind of opportunity.
References: https://help.salesforce.com/s/articleView?id=sf.customize_recordtype.htm&type=5