Adapting to changes in the application under test is a challenge as any modifications in the application's UI or functionality can break existing automated test scripts. This requires regular updates to scripts, making maintenance resource-intensive.

Incremental Integration Testing is a process where individual units or components of a software are integrated gradually to ensure that interface defects are detected and corrected. It helps in detecting issues that can arise during component interaction.

When a defect is first identified and logged, it is in the "Open" state. This means that the defect is now recognized and needs investigation or action. It has yet to undergo the various phases of the defect life cycle where its validity and resolution will be determined.

The "Defect Removal Efficiency" metric quantifies the effectiveness of the testing process in identifying and rectifying defects. A higher percentage indicates that the testing process was successful in catching and resolving a large proportion of defects during testing.

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.

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.

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.

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.

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 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.

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.

"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.