Heuristic evaluation and standard user interface testing differ mainly in their method of analysis. A heuristic evaluation is a usability inspection method where evaluators, usually usability experts, compare a software product against a set of usability principles or heuristics. In contrast, standard UI testing is often scenario-based.

The primary purpose of developing test scripts in automation testing is to enable the execution of tests repeatedly without manual intervention. This ensures consistent test execution, efficient regression testing, and helps in validating application functionality across different test cycles.

Regression testing ensures that previously developed and tested software still works after a change. Given the repeated nature of regression testing, Automated Regression Testing is a suitable approach as it can efficiently handle repetitive test cases.

The "Record and Playback" technique involves recording user actions as they interact with the application. The recorded actions then form a script, which can be played back later. This technique is helpful for novice testers as it requires minimal scripting knowledge but is not always scalable.

The "Defect Age" metric is a measure of the time between when a defect is introduced into the system and when it's discovered and resolved. It provides insight into how quickly a team identifies and addresses defects. MTBF (Mean Time Between Failures) measures the expected time between two successive failures of a system.

Usability testing is geared towards understanding how end-users interact with the software and ensuring a positive user experience. The primary considerations involve the system's ease of use, its consistency in design and functionality, and adherence to user interface design guidelines. UAT, on the other hand, determines if the system meets user needs, while load and compatibility have different focuses.

Cyclomatic Complexity is a white-box testing metric used to determine the complexity of a program. It calculates the number of linearly independent paths through a program's source code. A higher complexity score can indicate areas of the code that might be riskier or overlooked during testing, thus requiring more thorough testing.

Residual risk is the risk that remains after all risk response, mitigation, or prevention activities have been implemented. It represents the remaining threat even after you've taken measures to reduce the severity or likelihood of the adverse event.

Selenium is an open-source framework specifically designed for web application automation testing. It supports various browsers and languages like Java, C#, and Python. While other tools like Appium, TestNG, and Cucumber have their specialties, Selenium stands out for web automation.

In environments with tight deadlines and frequent releases, exhaustive testing isn't always feasible. Risk-based testing allows the team to prioritize critical areas and ensures that the most impactful and risk-prone features are tested first. This approach ensures better utilization of limited time and resources.