All amendments to the constitution must be approved at the end of a national convention assembled at the request of the legislatures.
The amendments are approved at the national level usually by congress and proposed to the states.
There are no "informal" amendments. All 26 amendments are approved by Congress and are part of the constitution. Your question makes the assumption that there are two constitutions and there isn't.
27
there are 35 amendments to the Kentucky constitution
a two thirds vote of congress
yes
yes
James Madison proposed 12 amendments to the Constitution, 10 of which were approved. The ones that weren't would have established Congressional representation and prohibited Congress from raising its own salaries.
true
Formal changes to the US Constitution are called Amendments. There are 27 in all. The first 10 are the Bill of Rights. Those ten and two more were added in the first few years after the US Constitution was created. Just 15 amendments have been approved in the last 200 years. That means the average time between amendments is about 13 years. Only 1 has been approved in the last 38 years.
It depends on the state, but often they are ratified through legislature or propositions.