Suppose I control Umbra Mystic and a land that's also an Aura.

(Note that I could find no combination of cards that could actually create an Aura land, so this question may just be pie in the sky.)

An opponent casts a spell to destroy the creature the Aura land is attached to. With totem armor, the Aura land is to be destroyed instead. Can I tap another land enchanted with Equinox to counter that spell?

My instinct is to say no, because the replacement effect adds a layer of indirection to the spell, such that the spell is not what destroys the land.

Conversely, suppose that a spell would normally destroy a land, but replacement effects (such as regeneration, shield counters, Pyramids or Void Maw) will prevent that. Can Equinox counter that spell?

My instinct here is also no, because the land will not be destroyed. But this seems to contradict my instinct for the previous case, because in that case we don't take replacement effects into account while in this case we do.

Suppose I control Umbra Mystic and a land that's also an Aura, possible through this convoluted method.

An opponent casts a spell to destroy the creature the Aura land is attached to. With totem armor, the Aura land is to be destroyed instead. Can I tap another land enchanted with Equinox to counter that spell?

My instinct is to say no, because the replacement effect adds a layer of indirection to the spell, such that the spell is not what destroys the land.

Conversely, suppose that a spell would normally destroy a land, but replacement effects (such as regeneration, shield counters, Pyramids or Void Maw) will prevent that. Can Equinox counter that spell?

My instinct here is also no, because the land will not be destroyed. But this seems to contradict my instinct for the previous case, because in that case we don't take replacement effects into account while in this case we do.