I defined it clearly, as all marxists do, as a classless, currencyless, stateless society in which the workers own the means of production at the “end of history” by the marxist materialist dialectic. I will not use any other definition because that’s the definition marx made…
I am aware of the End of History and it's more likely that society will shift towards libertarianism instead of socialism, considering how popular a brand is at being the US president and how everything regarding communism is already dead, or just capitalism painted red like what China does (see this community's icon as an example). I'd like to see socialism, something like UBI, but we're in a corporate world showing no signs of stopping, where brands are so prevalent that people flock to defend them without a second thought.
You're also using it wrong. Currency and the state have been a part of human society throughout history, from slavery to feudalism to capitalism. Implying that the End of History will somehow remove this need for currency and the state is a fairy tale and a misuse of The End of History.
What you're looking for is an apocalypse. -- Not that an apocalypse is automatically bad.
Marx never gave a specific implementation or even wrote about how it would be implemented… he merely gave a critique of capital and explained some inevitabilities about future societies based on these observations.
Yes, he did.

Furthermore I wasn’t even trying to argue with you, just inform you about communist belief.
Your belief on communism. Not communist belief -- yours.
where authoritarian methods were the most survivable because ruthless authoritarianism is very good at surviving despite the world being against it.
You're avoiding the question. Yes, that is the origin of communism in the soviet union. But by the time Stalin and even Lenin were dictators, why did they still require authoritarianism despite being in control of everything already? What purpose does the extermination of minorities and dissenters play in this magical communism you dreamt up? Wouldn't it serve better if they were at least somewhat democratic? Regardless, they fronted communism and were literally the faces of it, as much as that upsets your fluid definition of communism. It's really more of a religion you have here as opposed to society.
It’s not at all impossible to implement communism without a dictatorship, anarchists have done it countless times and then been destroyed by large capitalist armies throughout history.
Really? I can't think of any.
I think it’s possible but the conditions must be right, and I think your stance would have said the american revolution would be impossible.
I don't care about the US, it's a clown country and always has been.
See, your vagueness is really quite annoying. You don't say much of substance and leave everything up to the interpretation of others, leaving you a nice little window you can poke at because you've toyed them along; you've previously been called out on this multiple times. Here's you: Ah, yes, conditions, mm. Communist scholars, quite, quite. Methods, mm, yes, it's very convenient when I can use vagueness as a shield to hide behind. -- See how this is annoying? See how these don't answer anything? See how you don't actually say anything of meaning and leave it up to others to make up an interpretation, which is easier for you to dismantle since you haven't actually said anything of your own views.
I know how sealions work, and I'd like you focus only on the following question, again, but exact and honest this time. Tell me also what you think of Stalin, Mao, North Korea and tankie communities. No vague handwaving 'methods,' or 'reasons.' Those aren't answers. You need to be exact. Otherwise, I have no other option than assume you're arguing in bad faith, again, as above.