Question

Difference between regionalism and federalism

Answer 1

1- Federalism is a political concept in which a group of members are bound together by covenant (Latin: foedus, covenant) with a governing representative head. The term "federalism" is also used to describe a system of government in which sovereignty is constitutionally divided between a central governing authority and constituent political units (such as states or provinces). 
2- In politics, regionalism is a political ideology that focuses on the interests of a particular region or group of regions, whether traditional or formal (political divisions, administrative divisions, country subdivisions or subnational units). Regionalists aim at increasing their region's influence and political power, either through movements for limited form of autonomy (devolution, states' rights, decentralization) or through stronger measures for a greater degree of autonomy (sovereignty, separatism, independence). Regionalists often favor loose federations or confederations over a unitary state with a strong central government. 

So the most evident difference between the two is that federal units have more autonomy in governing their affairs (except for external relations and foreign policy which are competences of the federal government) than administrative regions... 

Federations: Canada, the United States, Mexico, Venezuela, Brazil, Argentina, Switzerland, Austria, Germany, Belgium, Bosnia and Herzegovina, Russia, the United Arab Emirates, Iraq, Pakistan, India, Nepal, Malaysia, Australia, Nigeria, Sudan, South Sudan, Ethiopia, Comoros, Saint Kitts and Nevis 
The rest of the countries are divided into administrative regions (terminology and range of autonomy varies by country).

Answer 2

Federalism

Federalism is the blended form of government, combining a comprehensive government such as the federal government with provincial governments in a legislative system.

Regionalism

Regionalism is a national doctrine focusing on the advancement of a federal or social arrangement which is based on one or more provinces which regulate financial advantages of a distinct region or the community of regions.