The primary goal of functional testing is to validate that each function of a software application operates in conformance with the requirement specification. For mobile apps, this ensures that all features work correctly and as intended, covering all scenarios including failures and edge cases.

Continuous Integration (CI) primarily aims to detect defects and issues early in the development lifecycle by integrating code changes frequently. By doing this, it ensures that software quality is maintained and potential integration issues are identified at an earlier stage, making them quicker and often less costly to resolve. This speeds up software delivery and ensures a more stable and reliable codebase.

"Photoshop" is a graphic design and photo editing software and is not typically used in the risk identification process in software testing. On the other hand, Brainstorming, Risk Matrices, and Flowcharting are common techniques and tools used to identify and visually represent risks.

In the Top-down approach of incremental integration testing, testing starts from the top or main module and moves downwards, incorporating sub-modules one by one. This approach allows testing of the main functionality earlier in the development process, even if all sub-modules aren't complete yet.

The Error Rate in usability testing refers to the number of errors users make when interacting with a product or system. A high error rate may indicate that the user interface is not intuitive or is confusing, necessitating design changes to enhance usability.

The principle that "Exhaustive Testing is Impossible" acknowledges that it's impractical to test every possible scenario due to constraints like time. In cases where time is limited, prioritizing test cases becomes crucial, focusing on high-risk or high-importance areas of the application.

The principle of "Keyboard Accessibility" ensures that all features and functionalities on a website or application can be accessed and executed using only the keyboard. This is essential for users who cannot use a mouse or other pointing devices effectively.

Stubbing involves creating a 'stub' or a simple implementation of the external component that simulates its behavior. This allows the function being tested to operate as if the external component is working, ensuring isolation in unit tests.

Penetration testing specifically evaluates a system's security by simulating cyberattacks. It aims to identify potential vulnerabilities in the system by seeing how it responds to malicious inputs. This proactive approach helps secure systems against real-world hacking attempts.

Voice Command Testing primarily focuses on ensuring that an application or website can be navigated and operated using voice commands. As voice-activated devices and technologies are becoming more prevalent, it's essential for web content and applications to be compatible with such methods to aid users with specific disabilities.