Network slicing is a core 5G technology essential for enabling diverse vertical services to share the same infrastructure. The H2020 5Growth project aims to extend baseline 5G management and orchestration platforms to manage the lifecycle of real end-to-end, reliable, and secure network slices with guaranteed performance. This paper details the 5Growth approaches to achieve isolation across network slices, provide secure interfaces for third parties, and leverage AI/ML for reliability through automated anomaly detection. The authors validate their slicing mechanisms through Proofs of Concept (PoCs) that involve interaction with ICT-17 infrastructure, moving towards full-fledged 5G pilots.