SF can connect social profiles to all of the following objects except __________.

Universal Containers wants to test code against a subset of production data that is under 5 GB. Additionally, Universal Containers would like to refresh this sandbox every weekend.
What type of sandbox should be used to accomplish this?

In a master-detail relationship scenario, the fields of the parent object need to be displayed in the related list.
How will a developer achieve this design?

The app builder at Universal Containers has been asked to ensure that when an Opportunity record exceeding $20k is being saved, details have been captured in the Comments field.
What can be used to meet this requirement?

When is it advisable to use a full-copy sandbox?