In a Waterfall model, where requirements are well-understood and not expected to change, the Quality Assurance phase can benefit from in-depth and comprehensive testing. Since the entire project is developed in a sequential manner, the focus can be on thorough testing to ensure the product meets quality standards.

In a monolithic architecture, the software is built as a single, unified unit. All components and functions of the application are tightly integrated into one codebase. This approach can be easier to develop initially but may face challenges with scalability and maintenance as the application grows.

In a microservices architecture, where various small, independently deployable services interact, integration testing is pivotal. It verifies that these microservices can communicate effectively and that the overall system functions correctly.

The Spiral SDLC model involves developing the project incrementally through a series of iterations. It emphasizes risk management and allows for changes and improvements throughout the development process.

Regression testing is typically performed after code changes are made and before a new release or update of the software. It ensures that existing functionality remains intact after modifications.

SQA helps in managing and controlling the software development process by identifying and rectifying process deviations. It ensures that the development process aligns with the defined standards and quality objectives, preventing issues and delays.

Using strict versioning with separate endpoints for each API version ensures backward compatibility while allowing for enhancements and changes. Clients can specify the desired version in their requests, and new versions can be added without affecting existing clients.

In the software development life cycle (SDLC), the planning phase is where the high-level view of the project is established, and its goals are determined. This phase involves defining the scope, objectives, and requirements of the project.

The primary objective of Unit Testing is to verify the correctness of individual units or components of a software system. It focuses on ensuring that each unit functions as intended and produces the expected output. Unit Testing is not primarily concerned with identifying design flaws, performance issues, or user satisfaction.

In white box testing, the "Code" is tested to check if it performs correctly. This involves checking that all statements and conditions in the code are tested, ensuring comprehensive code coverage.