The increasing complexity of automotive and embedded systems, particularly in the context of software-defined vehicles and electric vehicular platforms, has intensified the demand for robust fault tolerance, safety assurance, and cybersecurity integration. This research investigates the evolution and integration of dual-core lockstep architectures, redundant multithreading, and control-flow error detection mechanisms within modern embedded systems, emphasizing their application in safety-critical automotive environments. Drawing on a comprehensive set of references spanning hardware reliability, safety standards, cybersecurity frameworks, and emerging operating systems, the study explores how these techniques mitigate soft errors and enhance system resilience. The research further contextualizes these mechanisms within programmable system-on-chip platforms such as Zynq-based architectures and examines their performance trade-offs, particularly in terms of overhead versus fault detection efficiency. In addition, the paper critically analyzes the convergence of safety and security engineering practices, including ISO 26262 compliance and security assurance cases, to address vulnerabilities in cyber-physical systems. The rise of software-defined automotive ecosystems, including proprietary operating systems and electric vehicle platforms, is examined as a transformative force requiring integrated resilience strategies. Methodologically, the study adopts a qualitative synthesis approach, combining thematic analysis with technical evaluation of existing architectures and frameworks. The findings reveal that while lockstep-based approaches remain foundational for fault tolerance, their effectiveness is significantly enhanced when combined with software-level redundancy and system-level assurance methodologies. However, challenges persist in balancing performance overhead, scalability, and security integration. The paper concludes by proposing a holistic framework for resilient embedded system design, emphasizing co-engineering of safety and security, adaptive fault tolerance mechanisms, and alignment with emerging automotive software platforms.