If it is scotch then has to be in a barrel for a minimum of 3 years I believe. Then it will be tasted and they decide what to do with it. Mature it more, use it to be blended with other whisky etc

The age statement only relates to the youngest whisky in that bottle as well. For instance they could have 3/4 of the bottle filled with 50yo whisky, but to give it a younger taste and improve the palette of the whisky, they put 1/4 of the 25 yo in. As the 25 yo is the youngest, that is the age statement in of the bottle