What is true about Junction objects?

Universal Containers generates leads from three different sources: web, trade shows, and partners. Some of the information collected is applicable to all sources, there is also information that is unique to each type of lead. What should an app builder configure to meet these requirements?

Which API cannot be used to create the data model? (Choose three.)

Which functionality is NOT available on a custom object?

To Synchronize Accounts, orders and shipments in real time, a developer has built a custom interface between an external system and salesforce, prior to deployment, the developer needs to confirm that the interface can sustain the syncing of thousands of records at a time. Which sandbox environment is recommended to complete performance and load testing?