Arcanist and Preferred Spell and Greater Spell Specialization

[Feryn]

Would it require an arcanist to forfeit an entire "known" slot to use Preferred Spell? Essentially giving up the ability to cast that spell for the rest of the day to use it? Same with Greater Specialization?

[Feryn]

Was hoping to use this for PFS. I guess I should just wait and see what the ACG says.