When I was there in 2000, everyone spoke Russian, even the Ukrainians, so I’m not sure how you’d differentiate between them.
A lot similar to how throughout hundreds of years of revolts, both Irish guerrillas and British troops spoke English. In fact, during the American Revolution, both Patriots and Tories spoke English. Kuwait, like Iraq, was filled with Arabic speakers when it was invaded. Remarkable, isn't it?
“everyone spoke Russian, even the Ukrainians”
The Ukrainian adopted the ridiculous habit of changing the vowels in the Russian words, replacing “a” and “o” by “i” and “y”. Kiev becomes Kiyv, Kharkov became Kharkiv, etc. Other than that, there are no differences.
I understand Russian, and lately I was amazed to discover that I understand “Ukrainian” as well.