If the world uses a single currency, will the economy be more stable?
This is a very interesting question. The sovereign nations issue their own currencies and are taken for granted by many people, but few consider whether this is the economically optimal option.
I think it's possible but it will be hard to implement especially to poor countries. It depends on country whether the effect comes out good or bad. Each country has it's own basic needs and commodities. Agriculture and livestock will affect also as some country don't have those.