It depends on the type of research and where you are submitting the research.

Justifications are used for research results/findings. For research topics, you need to start with research objectives, problem statement, research questions, etc.

Can you be more specific? Business management research is a broad area and tomes are written about it just about everyday; Stanford University, California is a world leader in it. But what do you mean exactly by "justifying" the research? Are you talking financially? Academically? What's the angle?

Your research proposal is the framework required to justify your research in the field of business management.

Research model depends on the statement of problem. Do you mean that business models? if so apply latest business model called Sustainable business model through operationalizing it.