Spells you control may be countered by spells or abilities while Determined is on the stack, waiting to resolve.

The cards in the graveyard that you return as part of Bound's effect aren't targeted. They're chosen when the spell resolves. The creature you sacrificed may be one of them.

After Determined resolves, any spells or abilities that would counter a spell you control that turn will still resolve. They just won't counter that spell.

The creature is sacrificed when Bound resolves. It's not an additional cost. It's not optional. If you can't sacrifice a creature or a colorless creature is sacrificed, no cards are returned.

Split cards have two card faces on a single card. The characteristics of the half you didn't cast are ignored while the spell is on the stack.

If you copy a spell that's half of a split card, the copy copies that same half. For example, if you copy Assault, the copy is also Assault, not Battery.

If an effect allows you to cast a spell with certain characteristics, consider only the characteristics of the half you're casting. For example, if an effect allows you to cast a sorcery spell with mana value 2 or less from among cards in your graveyard, you could cast Assault this way, but not Battery.

To cast a split card, choose one of its halves to cast. There's no way to cast both halves of this split card.

A split card's characteristics are a combination of its two halves while it is not on the stack. For example, Assault // Battery has a mana value of 5 while it is in your library. If an effect allows you to search your library for a card with mana value 4 or less, you can't find Assault // Battery.

Each split card has two names. If an effect instructs you to choose a card name, you may choose one of those names, but not both.

Each split card is a single card. For example, if you discard a split card, you've discarded one card, not two. If an effect counts the number of sorcery cards in your graveyard, Assault // Battery counts once, not twice.