2 “Gravekeeper's” monsters Gains ATK/DEF equal to the combined original Levels of the materials used for its Fusion Summon x 100. While “Necrovalley” is on the field, this card, and any card in your Field Zone, cannot be destroyed by card effects. During your Main Phase: You can activate this effect; during the End Phase of this turn, add 1 “Gravekeeper’s” monster or 1 “Necrovalley” card from your Deck to your hand. You can only this effect of "Gravekeeper's Supernaturalist" once per turn.
No, Spells/Traps in the Spell/Trap Zone work the same way. For example, if a targeting effect is chained to the activation of an Equip Spell, you can send that Equip Spell to the Graveyard to activate Red-Eyes Slash Dragon's effect even though it hasn't resolved yet.
Amazing fusion, one of the most DOPE spellcasters ever