Suspension Field’s ability causes a zone change with a duration. It’s a single ability that creates two one-shot effects: one that exiles the creature when the ability resolves, and another that returns the exiled card to the battlefield immediately after Suspension Field leaves the battlefield.

If the target creature becomes an illegal target before the ability resolves, perhaps because its toughness was lowered, the ability won’t resolve and none of its effects will happen. No creature will be exiled, and Suspension Field will remain on the battlefield.

If Suspension Field leaves the battlefield before its enters-the-battlefield ability resolves, the target creature won’t be exiled.

Auras attached to the exiled creature will be put into their owners’ graveyards. Equipment attached to the exiled creature will become unattached and remain on the battlefield. Any counters on the exiled creature will cease to exist.

If a token is exiled this way, it ceases to exist. It won’t be returned to the battlefield.

The exiled card returns to the battlefield immediately after Suspension Field leaves the battlefield. Nothing happens between these two events, including state-based actions. Suspension Field and the returned card aren’t on the battlefield at the same time.

In a multiplayer game, if Suspension Field’s owner leaves the game, the exiled card will return to the battlefield. Because the one-shot effect that returns the card isn’t an ability that goes on the stack, it won’t cease to exist along with the leaving player’s spells and abilities on the stack.