For example, if Nethergoyf is in your library, its toughness is determined by the ability "Nethergoyf's power is equal to the number of card types among cards in your graveyard and its toughness is equal to that number plus 1." If your graveyard consists of an artifact card, a creature card, and an instant card, you won't be able to find Nethergoyf with Recruiter of the Guard since Nethergoyf's toughness will be 4
The rares are in the pool twice, then add the mythics
The target opponent doesn't choose whether to sacrifice a creature or not, although they do choose which creature they control to sacrifice
He cost 2 black and 3 generic, for a total of 5 mana and enters the battlefield with 5 starting loyalty
1 Blood for the Blood God
The additional mode you choose can't be the same as one you're already choosing with that spell unless that spell allows you to choose the same mode more than once