What are common debugging and testing challenges in embedded software development, and how can they be addressed?

When building a microkernel for an operating system, what are the most essential guidelines to follow, and how is a microkernel constructed? How does the modular method vary from the one you just explained, and what exactly are those differences? Which of these differences stands out to you the most?

What are microservices architecture and monolithic architecture in software development, and how do they impact scalability, maintenance, and deployment?

How can the use of model-driven development (MDD) and formal methods enhance the reliability and safety of embedded software?