As an additional cost to
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) this spell,
collect evidenceTo “collect evidence N” means to exile any number of cards from your graveyard with total mana value N or greater.
If a player is given the choice to collect evidence but is unable to exile cards with total mana value N or greater from their graveyard (usually because there aren’t enough cards to do so) they can’t choose to collect evidence.
A spell that has an ability that allows a player to collect evidence as an additional cost to cast it may have another ability that refers to whether evidence was collected. These abilities are linked. See rule 607, “Linked Abilities.” (CR 701.59) X, where X is the total mana value of the permanents this spell targets.
DestroyThe only ways a permanent can be destroyed are as a result of an effect that uses the word “destroy” or as a result of the state-based actions that check for lethal damage (see rule 704.5g) or damage from a source with deathtouch (see rule 704.5h). If a permanent is put into its owner’s graveyard for any other reason, it hasn’t been “destroyed.”
A regeneration effect replaces a destruction event. See rule 701.19, “Regenerate.” (CR 701.8) up to one target artifact, up to one target creature, up to one target enchantment, and up to one target planeswalker.