The problem with things like energy that are almost a necessity for modern life is that some individuals cannot afford it, not that "the economy" taken as a whole cannot.
Let's say 5% of Iran's GDP is spent on energy. Not sure what the number is, but whatever. A big chunk but affordable for the economy as a whole. At the market price, maybe 10% of people cannot afford to consume enough energy to meet the necessities of modern life - cooking, not freezing to death, using transportation. If you don't want these 10% of people to be shut off from modern society, you need to subsidize somehow.
It would be better to give the money to the people and they can choose to spend it on electricity or something else. Subsidizing electricity is a distortion.
2. It has always worked the same: people arbitrage the subsidy by doing energy inefficient labor. Bitcoin mining is just a more efficient arbitrage mechanism.
You're the guy that doesn't get invited to parties because you keep eating all the food because it's free, aren't you ?
All those subsidies are given under the expectation that people will behave reasonably and only use what is necessary, because it gets the country running. It's taking a hit so that your citizens can live and thrive. When you suddenly have a bunch of people running thousands of GPU for magic internet money, that is not a reasonable use of it.
In my opinion it would be better to have normal energy prices and simply redistribute the money. At least it would give an incentive to use energy more efficiently