I was looking at the translation page Ubuntu on launchpad: https://translations.launchpad.net/u.../+translations

There are a few things I'm wondering:
1. If a translation is complete, are they definitely going to add it to their releases? How are people supposed to install there?
2. I see that some languages are less complete than other, but then you do see these less complete ones be delivered with a release, but you don't see the more complete ones? Whats the deal with that?
3. Does every release of Ubuntu need new translations or do they copy everything that's the same from old versions to the new ones?