What are the matters considered in order to establish federal structure in Nepal

Explanation:

Where there already is a single nation (like France or Norway for two examples) there is no need for a federal system. It is only in nation-states that have a long history of local independent states (like the German principalities that had been largely independent from medieval times until the mid 19th century) or the United States if you count the 150+ years of our colonial era) that you find the need for such a system.

to phrase it more universally, federal government structures are needed when there are many competing local sovereign powers and you need to get them all working together in a system that is more unified than a confederacy but those local sovereigns are not willing to give up enough power to be forged into a single nation. Such a system may be necessary in cases of intense tribal animosities (like Iraq and Afghanistan) or where centralized power is an alien overlay (like India where the central government was imposed by the British) but absent factors like that I can not image why someone would want a federal system.

If Nepal falls under one of these scenarios, then the things to be considered are what powers need to be left at the national level - usually international issues and many economic issues - and which can be transferred to the local level - mostly tort, contract, criminal, and social issues. When can / should the national government be able to override the local governments and when can / should the local governments be able to tell the national government to butt out? How do you adjudicate those disputes?

Let me suggest that one read up on the origins of the different federalized systems throughout history and then come up with a specific list based on the realities in Nepal today. Then start building political alliances necessary to push through the changes - and if you have less than 70% public support (not merely apathy but active support)

you would travel west