Answer:
1. The two types of changes that came to my head first was that the states didt want to come together and also teh civial war that changed the states.
2. This goes along with the states becoming together. After the civial warnthe whole north side wanted teh south to change this included things like slavery.
3. The 26th, 19th, and 15th. They were placed due to the fact that it made it easier to elect a new president.