How do they determine Central Bank prime lending interest rates with the Euro? Is there a way they can stimulate the economy in one nation, instead of as a whole? And how do individual nations deficit spend, if they have no ability to control interest rates?

Prime lending rates are about 70% determined by global money flows and 30% by the blocs general economic performance.

Some ways a nation can stimulate its economy include micro reforms.For example subsides,tax breaks etc.