What is the difference between informal and formal amendment?

The difference between informal and formal amendment is that, the informal amendment does not actually change the Constitution itself. While formal amendment has a impact in the constitution.

That statement is true

A country could be categorized as a sovereign power if its government has a total control over their citizen. Such as what they have in North Korea
A country where the citizens have the right to directly vote their own leader can't be in any way categorized as a sovereign power