1. Yes, close interaction and empathy between all roles but especially disintermediation of the interaction between the development team and customers. This is more critical than tools or meetings.
2. No, Sprints are not required though timeboxing and general use of cadence is common. What is essential is reduction of batch size.
3. Yes, a closed feedback loop at the level of the product but also at the level of every step that is taken while building the next product increment as well as for the product development process itself.
4. Probably that biggest thing missing here is the emphasis on technical excellence and built-in-quality processes