About the Black Sea

An unknown element has not been yet formed in international relations of power. 
Ukrainian Orange Revolution fell as a result of the lack of Western and Eastern aid and support of Ukraine and its unsolved issue of "gas purchase". 
And on the 2008 Russo-Georgian War, separation of Abkhazia (with its inherent maritime territory over the Black Sea) and South Ossetia regions from Georgia by illegal war led by Russia is considered breach of international peace and security. And it is worth mentioning that Moscow has issued Russian citizenship for about 90 percent of residents of South Ossetia since then, according to the claim of Dmitry Medvedev. 
The non-planning revolution in Ukraine made the Crimean Peninsula which its area is more than double area of Cyprus to be separated from Ukraine. Needless to say, Crimea is not restricted to a piece of land but it involves part of the huge resources of Black Sea's energy. It is notable, the cancelation of Russia sanctions represents giving up the Crimea issue. 
Donetsk and Luhansk regions separation of Ukraine was also possible but the interference of the system prevented the implementation of this plan. Eventually, the issue of "gas purchase" was solved and the Minsk-2 agreement was also formed.