Using the definite article before a country/state name
Why do we write:
The UCI Road World Championships 2012 (when the year is mentioned)
The Republic of India (when there is only one nation) but NOT The India?
The Monaco Grand Prix (only one place which holds GP with that name)
Lake Baikal in South of the Russia (why not Lake Baikal in the Russia?)
I know the answer: The grammar usage is Definite Article but I'm looking for a clear explanation to this question.