Can I use Vulpix's or Zorua's "Ascension" attack on the first turn of the game?
Yes. This attack can evolve a Pokémon, even during the first turn of the game.
Source: PUI Rules Team (2004-06-17), TPCi Rules Team (2012-05-10)

Relevant cards

Note: All applicable cards may not be listed below.
PL1_44
PL1_63
PL4_46