The 4CaaSt project aims at developing a PaaS framework that enables flexible definition, marketing, deployment and management of Cloud-based services and applications. This paper describes the major challenges tackled by 4CaaSt for the comprehensive management of applications and services in a PaaS. These challenges involve the blueprint language to describe applications in the cloud and its lifecycle management, as well as a one stop shop for Cloud services and a PaaS level resource management featuring elasticity and advanced Network as a Service capabilities. 4CaaSt also provides a portfolio of ready to use Cloud native services and Cloud enabled immigrant technologies. The evaluation process followed to assess 4CaaSt progress is also described.