Was the breakup of the USSR and the Eastern Bloc nations inevitable (not able to be stopped)?

No the Eastern Bloc of Berlin was very unstable. Not only because the Russian and some of their former allies such as the USA started to have issues which caused a "cold" war in other words there was no fighting between both sides directly even tho they aided the North Vietnamese during Vietnam to destroy the US. Anyways when Germany lost the second world war Russia being Russia took half and left France, the US, and England to split the remaining half. Russia took it way to much for them to handle and with their strict visiting policy they treated the Germans badly keeping them confined to the city. Finally the US told Russia to tear down the wall and they finally agreed to. Over all Russia has never been to strong as a nation until the late 90s. Still as it stands their country is heavily run by the Mafia and other crime organizations. But yeah that should help.

couples could only have one child to reduce the population growth.

the three roles stated in the dialogue develop the siblings' personalities.

lloyd's personality looks like a trademarketer

dana's personality is afraid from lloyd's behavior and the oldest sister is a decided person who tries to solve any conflict