What are two features of Heroku Connect? Choose 2 answers

A business has a proprietary Order Management System (OMS) that creates orders from their website and ... the order. When the order is created in the OMS, an integration also creates an order record in Salesforce ... relates it to the contact as identified by the email on the order. As the order goes through different stages in OMS, the integration also updates it in Salesforce.
It is notified that each update from the OMS creates a new order record in Salesforce.
Which two actions prevent the duplicate order records from being created in Salesforce?
Choose 2 answers

A developer needs to join data received from an integration with an external system with parent records in Salesforce. The data set does not contain the Salesforce IDs of the parent records, but it does have a foreign key attribute that can be used to identify the parent.
Which action will allow the developer to relate records in the data model without knowing the Salesforce ID?

A developer needs to create a custom Visualforce button for the Opportunity object page layout that will cause a web service to be called and redirect the user to a new page when clicked. Which three attributes need to be defined in the <apex:page> tag of the Visualforce page to enable this functionality? Choose three answers.

Why would a developer consider using a custom controller over a controller extension?