Alrigthy, after thinking about it a little bit, here's what I have concluded:

(1) The Fredoast Federation is the legal predecesor of the Republic of Eflad. It was founded in 1355. Then 485 years of enslavement and discrimination of the native happened resulting in the Civil War which consequently resulted in the founding of the Republic of Eflad.

(2) Because Eflad was puppet state of the Frankists in the Great War, which was around 1940 and officialy lasted to the end of the war untill they were defeated by the partisans, which resulted in a new constitution. Does this mean that a new state was created as a legal successor or that the Republic of Eflad continued to exist? The government could have moved somewhere so that the RoE continued to exist just conquered and then after the war, they returned and built the country back up.