p.s Does Alice count as a yokai? I know she isnt human but the people in makai were devils i think- does that count as a type of yokai? And her mom was the godess so maybe she isnt a devil either - or half devil half god? who knows..
Yes, magicians who perform life extending rituals become youkai. Abandoning part of your humanity is viewed as a negative thing. Thus they are viewed as some form of evil.
Has it ever been stated Alice performed those life extending rituals? If she was created as a devil by her godess mom she wouldnt NEED to do such rituals - devils probably live as long as yokai.
Also- she didnt GIVE UP any humanity even if she did cast them because she never WAS a human.
I never got the impression she had cast them anyway or needed to- she is always portrayed as being very young- probably the same age as marisa and reimu- and also not advanced enough as a new witch to cast that sort of spell.
And if she was never human anyway she wouldnt even need to.
She was a human. That was stated in Perfect Memento in Strict Sense. 'She is the type of magician that was originally human and became one through training.'
Also in Perfect Memento in Strict Sense there are more general informations about magicians like:
'In the case of those who were originally human, in continuing their study of magic, it is when they learn "abandon food" magic that they become magicians.'
Thus she had to complete this ritual and since its also stated that she eats and sleeps although she no longer has to do so, we can conclude that she did that complete 'Abandon food'.