Question

distinguish between coming together federation and holding together federation

Answer 1

Coming together federation is one in which individual states come together to cooperate and allie into one nation to share benefits and govern themselves as single Nationals. Thus they give dual citizenships to their residents, one for the state and the other for the country.
Ex: USA
Holding together federation is one in which a central government holds it's various diverse parts of the country knows as states and supplements them. They only have a single citizenship.
Ex. India

Hope this helps!