UP is the Ultimate Power, yes. It unlocks at level 8 and makes you lose all benefits from that blend until the next day.

You get one blend per day, or more if you already have the More Flavors class feature, and it lasts all day (or until you use its UP).

No blends that give breath weapons. I dislike how having that qualifies you for poorly written metabreath feats and I dislike the shenanigans you can do with that. However, look up the "A Breeze of Life and Death" ability under (Un)Holy Smoke. That's very similar to a breath weapon.