Hi,
Rivne is in today's West Ukraine but it was part of the Russian czar empire until 1917.
Then it was part of Polish Wołyń 1920-1939
Your Euhenia was born Palczewska there, so that's a Polish name but she was Ukrainian & Orthodox religion.
Iwacewicze are today in Belarus, Brest area, It was also Polish 1920-1939 when your gma Valentina was born there. She was also fluent in Ukrainian (her mother tongue) but also spoke some Polish.
Do you know any family stories of these 2 and Valentinas dad when they were living in Polish Belarus and in the Russian empire?
Do your parents and other relatives have their own birth certs? If yes, you can prove your family relationship to Valentina and Euhenia. Normally with your birth certs you would be able to contact the state civil archives of Belarus or Ukraine.
But obviously..
The problem is the current war in Ukraine, and also the dictatorship in Belarus.
Perhaps you can locate the embassy of Ukraine closest to you and ask there if they can guide you. Be prepared that you also need to pay fees to the archives for finding any info for you.
A shot in the dark would be gathering your birth certs and asking a Polish state archive about any pre WW2 info about them, but for that you need the family stories of where they were living on Polish soil.
_________________ Pozdrawiam serdecznie,
Anna (Annuszka G) Veganova