The president was elected by MASSIVE fraud. No one had the courage to do anything about it until things came to a breaking point last fall.
No, the 2010 election was run according to the Ukrainian constitution and Yanukovich emerged the winner. Lots of people/organizations certified the result. Maybe you're thinking of the 2004 election which the opposition claimed was fraudulent and was subsequently over turned by the so-called Orange Revolution.
My argument about the legitimacy of the interim government will play itself out if eastern Ukraine decides to secede from the west, because it provides them with the casus belli for the break. Then it becomes a question of whether divorce will be amicable or not, and whether the nationalists in the west decide to break away themselves.