If a sorcery card gives -X/-X to a 1/1 creature till end of turn does the creature die?

Question

1. I use Urge to Feed (-3/-3 until end of turn) against a 1/1 creature, does that creature die?
2. If I use Zealous Persecution in a multiple player game, would it destroy all 1/1 creatures on the battlefield except mine?
3. If I use Dead Weight to enchant a 1/1 creature, would it destroy that creature?

I am confused with the first 2 because it says "Until end of turn", so would the 1/1 creature go back to normal after my turn?

For the 3rd one, if it does destroy the creature then would the creature come back to life if the enchant is destroyed?

Answer 1

The creatures die in all of those cases. If a creature's toughness is reduced to zero (or less), it is immediately put into the graveyard. It doesn't matter if at the end of the turn its toughness would become positive again; it died long before then. There's no coming back from the dead (not without playing a card like Unburial Rites, anyway). In the third case, when the creature dies, since Dead Weight no longer has a creature to enchant, it also immediately goes to the graveyard.

If you care about details of the rules, this is an example of a state-based action. Here's the actual rule:

704.5f If a creature has toughness 0 or less, it's put into its owner's graveyard. ...

State-based actions happen automatically*; others you already know include creatures dying when they've taken lethal damage or you dying when your life is zero. Another state-based action: auras being put into the graveyard when the creature they enchanted dies (like I mentioned with Dead Weight).

One more general thing you should learn here: when an object changes zones, like a creature being moved from the battlefield to the graveyard, it doesn't "remember" anything about where it came from. The creature card in your graveyard doesn't know it used to be a creature on the battlefield, that its toughness was reduced, and so on. It's just in the graveyard, and it stays there. (If you're curious, this is comp rule 400.7. - it does have a few specific exceptions, mostly things that you'd expect are necessary to make cards work.)

_{* State-based actions don't technically happen immediately; they happen whenever a player would get priority. This distinction doesn't usually matter, though - pretty much, it means the creature dies when the spell or ability finishes resolving, not halfway through, which doesn't usually make a difference.}