To pay the 1 and get DS back, does it matter what else is in your GY as long as you have Spark below a Creature? Like would this setup be legal for me to return DS at my upkeep:

Instant

Artifact

Sorcery

Goblin Rock Sled

Death Spark

6 other cards

Old designs that use the physical position of a card are so bizarre lol.

The “top creature card in your graveyard” is the topmost creature card of all creature cards in your graveyard, ignoring cards of other types.

Note that if you’re playing with cards like Barrow Ghoul that care about graveyard order, you won’t be able to reorder your graveyard at all unless a card instructs you to do so.

A spell goes to the graveyard as the very last step of its resolution, so it will be on top of your graveyard.

For example, if you Thought Scour yourself, the two cards you mill from Thought Scour will go to your graveyard, then you’ll draw a card, then you’ll put Thought Scour in your graveyard.

Yes.

Commander uses cards from the whole span of Magic’s history and there are at least 20 cards in Magic’s history that care about the order of cards in your graveyard or another player’s graveyard.