QIf I look at the top 2 cards of my deck and find a Hunter card, can I choose not to reveal it and add it to my hand, and instead bury both cards?

AYes, you can.

QIf my opponent has a Servant of Usurpation on their field, and I play this follower's Last Words ability during their turn, will Servant of Usurpation's "During your turn, whenever a card is put from an opponent's deck into the cemetery" ability trigger?

AYes, it will.