1. No, the USSR, Russia nor China have never established what I am suggesting: a kind of enterprise structure at the base in which the collective of workers share a common task in addition to their different positions within the enterprise's technical division of labor. The common task would be to receive and distribute the net revenues of the enterprises, to perform, in short, what boards of directors do now. For the full analysis of how and why the USSR (and likewise China, et al) never did this in a society-wide basis, see S. Resnick & R. Wolff, Class Theory and History: Capitalism and Communism in the USSR (London ad New York: Routledge Publishers, 2002).
2. Socialism in the Marxian framework of analysis, refers to how production is organized. It means that the workers whose labor generates a surplus (an excess above what the workers themselves get back out of their output for their own consumption) are also identically the collective of persons who receive and distribute that surplus. Socialism is the negation of exploitation where exploitation is defined as an organization of production in which the people who receive and distribute the surplus are different from those who produce it. Examples of exploitative organizations of production include slavery (masters exploit slaves), feudalism (lords exploit serfs) and capitalism (employers exploit employees). If production were transformed from a capitalist to a socialist form - and exploitation were thereby eliminated from society the way slavery and serfdom were earlier - that would leave open the question of how society would distribute resources among productive enterprises and likewise how society would distribute the outputs of those enterprises. This could be done by markets, state planning, planning by other social institutions, and so on in an endless array of combinations. Markets have co-existed with every other kind of organization of production (e.g. slavery, feudalism, etc.) and the same is true of planning, and have always partly reinforced and partly undermined the organizations of production with which they coexisted. I would expect the same if markets coexisted with socialist organizations of production.
3. There is a world of difference. A capitalist industrial corporation (Marx differentiates that from a merchant or financial corporation) is one which gets from its productive employees a value of output that is larger than the total value paid by the corporation for physical inputs (tools, equipment, raw materials) plus the value paid to the workers as wages (payment for what Marx calls their labor power). The difference is the surplus value appropriated by the corporation's board of directors. In the mainstream definition taught in schools (and by me as a professor) there is no such thing as a surplus and hence what I just described is NOT an aspect of the corporation, let alone its central aspect as for Marx. For more information take a look at an extended discussion in S. Resnick and R. Wolff, Knowledge and Class: A Marxian Critique of Political Economy (Univ of Cgicago Press, 1987, chapter 3).
4. For the last half century it was taboo to question or criticize capitalism in the US; the very few who dared to do so were immediately branded as either crazy, ignorant, or agents of communism. For 50 years the vast majority of Americans heard nothing but endless praise for capitalism and no serious discussion of any alternatives. The result was a capitalism without criticism or many limits, a capitalism that could and did indulge its darkest anti-social tendencies. That is one reason why US capitalism collapsed in 2007 and provoked a crisis that has now spread globally with no end in sight. US capitalists were so shocked by the regulations and taxes on them passed by Roosevelt in the 1930s Great Depression that they have worked since the end of World War II to undo the welfare state type of capitalism ("capitalism with a human face") Roosevelt created. They have done that by destroying the labor movement (it has had a steady decline sine the 1950s so that now under 7% of private sector workers in the US are unionized). They likewise destroyed all the socialist and communist parties who had worked with the unions to win the welfare state type of capitalism in the 1930s. The twin results have been (1) a neo-liberal capitalism replaced the welfare state especially after the 1970s and (2) that neoliberal capitalism has now crashed the global economy again but this time with no effective labor movement or left wing counterforce as there was in the US in the 1930s. And that situation poses the gravest possible dangers for the world.