1) The Skin will not work on EU.
"Sadly no, the codes are just for NA, the wont work in our platform."Solapaine, Player Support Specialist, via the official EU forums.
2) The skin will be made available for "normal" purchase later.
"PC Gamer gets this skin first as a temporary exclusive. It will be made available in the store at a later date."the official forums.
3) The code, much like any other skin code, WILL unlock the champion on your account if you do not have her already unlocked. I don't have a source for this aside from the multiple skin codes I've redeemed ( ala Pax Jax, Pax Sivir, Viking Tryndamere, etc ) that unlock the champion as well.
4) Magus is not "Magus, The Magus Ascendant" real name.
At the time this issue of PC Gamer was published, we didn't have a finalized name.RiotRunaan, Associate Writer, via the official forums.
"The Magus Ascendant" is only his title. His name is not "Magus."