No, millions of Poles have not had the chance to "studied and worked in Belgium/Netherlands/Finland" while under Russian occupation.
- You werent able to cross to the west unless on official Government delegation.
- You werent able to cross the border _at all_ unless Government decided to let you. It was a political decision by a party committee.
- Vacations abroad were only possible as an official reward from the Government, and never outside ~Comecon.
- You couldnt even keep a passport in your own house. It was given to you before departure, and you had 7 days to return it after crossing back.
You know who did work and study in the west? People who ran away https://en.wikipedia.org/wiki/300_Miles_to_Heaven https://en.wikipedia.org/wiki/The_Last_Ferry
My uncle actually planned stowing away on a ferry to Norway in 1981, but got caught in the port and landed in penal company.