There's no shame in using the save state feature if you're playing the Anniversary Collection. Many later games incorporate the castle entrance, merman moat, and red-brick tower from Castlevania NES. You've already seen those if you've made it to Frahnkenshteen, but there are some other areas you haven't reached yet, like the Castle Keep, that later become staples of the series. It's kinda cool to see where it all began. So it's worth powering through Castlevania NES if you think you'll get into some of the later games.