Yes, JPY is a hard currency. Its a 3 most traded currency(1st one is US Dollar) by value in the world, it has 19% daily share in traded currencies.

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The phrase "hard currency" is normally only applied to strong, stable, easily exchangeable currencies. This would include the US Dollar, Euro, GB Pound, Japanese Yen and several other currencies.

Examples of non-hard currency would be things like the Zimbabwe dollar - where the notes are difficult to exchange for another currency and where the countries inflation makes the notes worth less each week.

When hard currency is not available for a country to use it can barter product s and goods for other products and goods. Bartering accounts for about a quarter of international trade.

No, they only have the Euro. That would be really confusing to have the Euro and another currency. It is hard enough with just the Euro.