So just to clarify, should a character with The gift have all there Supernatural Abilities (for example Sense Holy/Unholy) associated with the Magic Realm?
Thanks to Saulot for drawing this to my attention! 
cj x
Concerning the Gift and supernatural abilities: Not necessarily. The Gift is Magic Realm, but some supernatural abilities could come from other Realms (Infernal, for instance...)
Well, it's sorta related...
No.
This is specifically addressed... somewhere in the core rulebook*. Each such virtue must be so associated, but each could be associated with a different Realm.
(* Edit - in the section on Virtues, last par on p 36.)
More, each such association means that a character takes no Warping from spending time in a high Aura of such, so in theory could be immune from all 4 Realms, if that's your idea of a good expenditure of Virtues. (Other sources of Warping are still valid, such as high-level burst effects or any continuous effects, etc.)
Note that this quote is for Virtues acquired, not learned through The Gift.
I wonder if demons have been able to learn all about the Parma Magica.
I've been pondering this as I am planning a saga involving the Damhan-duidsan. How do magi Ex Miscellena in this tradition with Incantation as their non-Hermetic Major Virtue use it in conjunction with Hermetic Magic? Obviously infernalists use it together with Unholy Powers, do magi do something like add Communication to spellcasting rolls instead of Stamina, add the Ability score when doing naughty stuff, or what?