MTG - Does this do an infinite combo? Devil's play + Sevinne Chronoclasm + Geistblast from graveyard + Twinning Staff
No, because Geistblast is not cast. Its ability

{2}{U}, Exile Geistblast from your graveyard: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

is an activated ability, not an alternative casting cost. Therefore Sevinne is not triggered and your chain falls apart at step 3.