12 May 2023
If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are performed.
12 May 2023
You cast the copy while the ability is resolving and still on the stack. You can't wait to cast it later in the turn.
12 May 2023
Because you're paying the spell's costs, if the spell has {X} in its mana cost, you may choose its value as normal.