Lady Sovereign is from England.
Generally, "constituent country" is a term applied to territories that call themselves countries, that are a part of a bigger sovereign country. For example, England is a constituent country of the United Kingdom and Greenland is a constituent country of the Kingdom of Denmark. If you mean a sovereign country within another sovereign country, that is called an enclave.
It means that was the official day of creation of your country as a sovereign unit
North Korea thinks that it is Sovereign. But they are not.
Yes
Canada is an independent country.
China is not in any country. It is a sovereign country in its own right.
One of the many definitions of "Sovereign" is, the reigning Monarch of a country. Englands current Sovereign is Queen Elizabeth II.
None. Bulgaria is a sovereign country itself.
It is an independent sovereign state.
Italy is a sovereign country.
A sovereign state.