Its what it says on the tin, what is the earliest point in history that we can reach an independent Belarusian state
We are defining a sovereign Belarusian state as
A) National language is Belarusian
B) The major culture group is Belarusian
C) It operates as completely independent/semi-independent from any neighboring state
The issue here is juggling when the Belarusian people came into their own and the concept of self-determination, at least to me