Functional devolution will mostly relate to the delegation of functional aspects of an entity.

Functional - The ability to carry out a purposeful activity. and
1.Devolution - a term used to describe how responsibility for the development and management of public policy and services is changing.

Devolution is a single word used to describe a process. It is a quick way to say, "the movement of authority and responsibility for public policies and services from a national to a local level of government."
2. devolution is advisable for central state to practice it because more autonomy is given to the local government units and therefore they can implement policies and laws faster and more efficiently because they don't have to wait for the go signal from the government.