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.

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.

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.

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.

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.

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.

The "Test Plan" is a comprehensive document that outlines the scope, approach, resources, and schedule of testing activities. It serves as a blueprint for all testing processes and activities, ensuring that every aspect of the testing process is covered and understood by all stakeholders.

"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.