A company has a native iOS app for placing orders that needs to connect to Salesforce to retrieve consolidated information from many different objects in a JSON format. Which is the optimal method to implement this in Salesforce?

A developer has a Batch Apex process, Batch_Account_Sales, that updates the sales amount for 10,000 Accounts on a nightly basis. The Batch Apex works as designed In the sandbox. However, the developer cannot get code coverage on the Batch Apex class.
The test class is below:

What is causing the code coverage problem?

A developer is asked to find a way to store secret data with an ability to specify which profiles and users can access which secrets.
What should be used to store this data?

Consider the controller code above that is called from a Lightning component and returns data wrapped in a class.

Consider the controller code above that is called from a Lightning component and returns data wrapped in a class.
The developer verified that the Queries return a single record each and there is error handing in the Lightning component, but the component is not getting anything back when calling the controller getSomeData().
What is wrong?

A developer is asked to look into an issue where a scheduled Apex is running into DML limits. Upon investigation, the developer finds that the number of records processed by the scheduled Apex has recently increased to more than 10,000.
What should the developer do to eliminate the limit exception error?