What is true about validation rules? (Choose all that apply.)

Universal Containers uses a custom object to track expense reports. They would like to automatically post updates on a record's feed whenever an expense report has been approved.
What social feature can be used to accomplish this?

Which of the following is not a valid return type of a custom formula?

An admin is trying to add a custom VF page to the mobile app quick navigation menu but can't.
What might be the problem?

On the Account Lightning record page, users need to see ten fields and the ability to sort and wrap text on their Related Lists.
What Related List type would the app builder select for the Related List Lightning component?