1. Most of the time Kdramas are filmed as they air. That's why when some dramas are extremely popular, they might be extended by 1 or 2 episodes (an example is The Red Sleeve that is currently airing). Sometimes the drama might have completed filming before it airs like My Roommate is a Gumiho that aired this year.
2. There are different titles because sometimes the Korean title can be translated to English in multiple ways. There are also some dramas where the Korean title doesn't give an idea about the drama or make a lot of sense in English so those dramas get an English title