1. The USSR "question" as it were is extremely complicated. On the one hand, you have a society whose GDP expanded at an incredible rate post civil war (over 1,500% in the space of 20 years) and a corresponding incredible reduction in illiteracy and poverty, and on the other hand you have the completely self-inflicted wounds of the failure to collectivize agriculture, what I like to call the Internyet problem (Soviet computer scientists - who dubbed themselves then Cybernetics technicians) plotted out how to create a network of computer systems using phone lines in the 1950s and set about working out how such a thing may be done - it actually caused a very real crisis within the CIA and NSA in trying to figure out a way to counter the untold amount of influence and productivity that such a thing would create - however the entire project was sabotaged by the Soviet military, from the stagnation and reliance on oil that came in the late 70s and 80s.
If one wanted to fix what the "main" problems for Soviet economic development were it was these as follows: truncated access to the international markets due to being an international pariah (outside pressure), failure on the part of the Soviet government to make *most* of the nomenclatura (government officials) accountable for misdeeds and failures, failure on the part of the Central Government to ameliorate conflict between government agencies (the conflicts between the statistical bureau TsSU and GOSPLAN are legendary and the repercussions were felt throughout Soviet society), and an over-centralized government in general.
The primary cause of the collapse of the USSR however, was the stagnation and lack of faith in the Communist Party of the Soviet Union to continue leading. For example in today's China, while life isn't perfect, *most* people have at least some amount of faith that the Chinese Communist Party and its 7 subsidiary/fraternal parties that rule China have *some* idea what they're doing. As such it's unlikely that that government will collapse given that it's fairly easy to point out the improvements in Chinese living standards for a huge amount of people over the last several decades. The Soviet Union *was* able to do the same until the 1980s, when suddenly bread lines began to form, Chernobyl exploded, and the Soviet Army that had defeated Nazi Germany failed to achieve victory in Afghanistan. As such there was a massive and sudden loss of faith in the CPSU that lead to there being fertile ground for the staging of a coup that overthrew the Soviet government.
How that could've been "fixed" is mostly just a guessing game and hypotheticals that I don't really have much of a desire to get into because it's just pissing into the wind really. All there is to do is to understand what the failures/mistakes were.
2. Socialism "taking" from the rich
I fail to see how a redistribution of wealth isn't an engine for growth - increasing the wealth of the majority of one's economy causes a spike in demand (demand side economics) that fuels growth out of hand. Again though, the goal of Socialism/Communism is not a *completely* equal society where everybody makes the same - it's about *access* to the produce of society being equal, not necessarily having all the same stuff.
3. People do all sorts of stuff for all sorts of reasons. The Soviet Nuclear Program prior to 1937 (when they shifted from civilian power applications to weapons) was highly advanced, as were their RADAR, rocketry, and aero industries; not to mention other technological and scientific achievements. I should point out that *many* times in capitalist societies people who actually invent things aren't greatly rewarded for doing so, as the intellectual property is often retained by the company itself - granted you may receive a raise or perks - but the company will by and large maintain the lion's share of the profits from your invention - people make cool shit because they want to make cool shit, often without the motivation of becoming rich. Just look at all the things people have made and done for TF2 with minimal expectations (or none) of being paid back. I should also point out that *most* work environments the world over aren't exactly democratic - but still production and advancements are made, and entrepreneurial activity continues within them.
4. Supply and Demand still exist, but you simply ignore the prospect of making profit. See in a standard supply-demand graph you attempt to find "equilibrium" which is the point at which supply and demand meet at an optimal spot for an optimal rate of profit (if making a profit is possible to begin with). The *cost* of overproduction is that you take a net-loss on this production for the producer - but since states can gather money by taxation, borrowing, printing money, bonds, and myriad other means, they don't have to care whether or not they take a net-loss on production. This will in turn, on the monetary side, cause inflation (which is why most socialist economies have very high inflation rates). This isn't a problem so long as you carefully manage the situation so as not to cause hyper-inflation or come up with other effective means for distributing produce. Very large companies do the same by selling stock to temporarily raise their cash flow to enable them to sell goods at a net-loss to themselves, or once they corner a market they "take it back" by selling some related piece at an artificially high rate - Caterpillar machine parts (vs. the machine which is sold at a net loss) or an Xbox 1 (which is sold to the user at a net loss to Microsoft) and its games (which are inflated to a massive amount to make up for the loss on the console). A socialist state engages in the same behavior, but they use other means (for example in the USSR and contemporary Venezuela they used oil revenues to finance the net loss - which works just great until oil prices suddenly collapse). They key is to not get caught with your hand in the cookie jar - which is extremely hard to do, but not outside of the realm of possibility (for example Norway does much the same with its oil revenue but they diversified state interests enough to not wind up in an economic cataclysm when oil prices fell).
5. That's part and parcel of a trade oriented monetary policy. A "strong dollar" only helps if you intend to buy lots of stuff from other people - but "strong" sounds good. When you have a significant portion of the economy which is operating on the government's bill, or is being sold on the international market (at a higher price than could be sold at home) a weak currency has massive benefits because you obtain "stronger" currency that you can use on the international market with all of the benefits that it brings, while at the same time ensuring you sell more of your goods abroad. The only time it can hurt you is if your country is incapable of producing certain goods and can't obtain sufficient foreign currency reserves to compensate for this lack.
That situation played out in the USSR throughout its history - in particular post 1927, when the five year plans called for massive industrial projects, but the USSR itself didn't have the means or skilled tradesmen required for such industrialization, *nor* did it have foreign currency reserves to use to bring in skilled technicians and expensive foreign tech, so what they did instead was pay in gold bullion and national treasures. A tactic that becomes less and less effective with time, as gold flooding international markets reduces the price of gold, and a nation only has so many national treasures to pawn for foreign currency.
Again you could also print enough money (devaluing your currency) to cause hyper-inflation which is bad, but China doesn't appear to be anywhere near that their goal appears to simply make sure that their currency is weaker than the Euro and the Dollar.