I reject to understand why Lithuania, a part of civilized Europe use such dirty methods not suitable for a member of European Union.
First thing you should know is that western Europe (ie EU) isn`t that civilized. And why are you surprised with Lithuania? Look at Croatia. Its actually Greater Croatia with Nazi regime, while EU arranged Serbs to be blamed. Same thing in Bosnia where now rule sharia law, Nazi-Islam ideology and where EU even took part in populating Arab mujaheedines there. Or look Albania and Kosovo (province in Serbia illegally seceded) where also rule Nazi-Islam plus narco mafia.
wild countries like Belarus and Ukraine could hold something they got illegally
Belarus isn`t wild. They finally got their independence. I am sure, quality negotiations between Poland and Belarus could be in place, for all open questions. With Ukraine is different because EU there installed Nazis. But, things would one day improve when bandersits are past and then, negotiate.