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.

Continuous Delivery focuses on ensuring that code changes can be deployed to production at any time, making the release process reliable. Continuous Deployment, on the other hand, ensures these changes are automatically deployed to production frequently without human intervention.

While Load Time, Response Time, and Throughput are common metrics used in performance testing to measure various aspects of the system's performance, "Number of Defects" is not a performance metric. It is typically associated with functional testing and bug tracking.

Error Guessing is a testing technique where testers rely on their past experiences and knowledge of system failures to identify potential defects. Instead of using a systematic approach, testers use their intuition to "guess" where defects might be present and construct tests based on these hunches, drawing from previous issues they have encountered.