Why is Ukraine a full member of the UN and had been since 1945?
That is news to me. Perhaps because all the so called USSR "Republics" had full membership?
Anyway, Ukraine had dozens of USSR nuclear missile launch sites before the USSR collapsed around 1990.
Besides the U.S.S.R. itself, both Ukraine and White Russia (Belarus) had seats in the General Assembly.
The justification for giving Ukraine and White Russia - both of which, after all, belonged to the U.S.S.R. - their own seats in the General Assembly was that they had suffered "special suffering" in WW II.
Make of that what you will.
Regards,