The lookup relationship will need to be converted to a master-detail relationship before a roll-up summary field can be created. This is correct because roll-up summary fields are only available on the master object in a master-detail relationship, and a lookup relationship does not establish a parent-child hierarchy between the objects

To display the actions on the Lightning record page, two components could be included on the layout:
Highlights panel: The highlights panel displays key information and actions for a record based on the compact layout. Users can see and perform actions such as edit, clone, delete, follow, etc. from the highlights panel. [Source] Activities: The activities component displays tasks and events related to a record. Users can also create new tasks and events, log calls, send emails, and view past activities from this component.

Highlights Panel. This is correct because the highlights panel component displays key fields from a record at the top of the page, and it can be configured to show up to 10 fields.