原文When Photon Blast Barrage's first ability resolves, it creates X copies of Photon Blast Barrage. Those copies are created on the stack, so they're not "cast." Abilities that trigger when a player casts a spell won't trigger. The copies will then resolve like normal spells, after players get a chance to cast spells and activate abilities.
原文Photon Blast Barrage's first ability resolves before Photon Blast Barrage itself. It resolves and creates copies even if Photon Blast Barrage was countered or has otherwise left the stack.
原文Each of the copies will have the same target as the original unless you choose new ones. If you can't choose a new legal target, then it remains unchanged (even if the current target is illegal). If there are multiple copies, you may change the targets of each of them to different legal targets.