No country in history has implemented communism in the strict sense of the word.
As for the success of socialist principles of economic management (i.e. common ownership of property/means of production), it varies (there's Norway, and there's Venezuela), much like the success of capitalist economies varies.
Of course not. Oppression is baked into the system. It's by design. Marx explicitly describes it as necessary for abolishing the capitalist state and suppressing those who would undermine by attempting to engage in individual market activities.
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No country has had true scotsmen, either.
Every country has had communism that I say has had communism.