One is with the succubus teacher in Transylvania. You'll need to have learned the cock growth spell!
Otherwise, there's a bad end involving it if you get captured by Mistyra
Hmmm, that should be everything. Maybe double check that all this stuff you listed if there? Also if you don't have enough mana to cast the spell, it'll be disabled. But you'll be able to see the options listed when you defeat her
That stuff will more likely be end of route type rewards instead of something you can get just anywhere