This paper presents the Quest real-time operating system (RTOS) and Quest-V partitioning hypervisor for mixed-criticality embedded and cyber-physical systems. It explores how Quest-V can co-host multiple Quest RTOS instances alongside Linux while partitioning CPU, memory, and I/O resources. The paper also introduces the Quest SDK, which supports rapid development, testing, and debugging of applications using secure and predictable shared-memory communication between operating systems.