Ojutai's Summons

At the beginning of your upkeep, all delayed triggered abilities created by rebound effects trigger. You may handle them in any order. If you want to cast a card this way, you do so as part of the resolution of its delayed triggered ability. Timing restrictions based on the card’s type (if it’s a sorcery) are ignored. Other restrictions, such as “Cast [this spell] only during combat,” must be followed.

Rebound will have no effect on copies of spells because you don’t cast them from your hand.

If a spell with rebound that you cast from your hand doesn’t resolve for any reason (either because another spell or ability counters it or because all its targets are illegal as it tries to resolve), none of its effects will happen, including rebound. The spell will be put into its owner’s graveyard and you won’t get to cast it again on your next turn.