If Russia continues to pursue the path she has followed since 1861, she will lose the finest chance ever offered by history to a nation, in order to undergo all the fatal vicissitudes of the capitalist regime.

Marx thought Russia had a unique opportunity to sidestep capitalist development, and kick off revolution in the west. He made it clear that if conditions continued as they had, however, that this opportunity would never materialize. I've read Capital and its post-scripts, I've read his letters to Russian revolutionaries. I used to be an anarchist, and these get thrown around all the time to make it seem like Marx was supportive of anarchism at the end of his life (which he wasn't). This isn't new information to me, you're just confusing Marx saying Russia had a great opportunity to skip capitalism with Marx saying he thought Russia would in fact do so.