Polymorphous Rush

If all of the spell's targets are illegal when the spell tries to resolve, it won't resolve and none of its effects will happen. If one or more of its targets are legal when it tries to resolve, the spell will resolve and affect only those legal targets. It will have no effect on any illegal targets.

If the creatures copy a creature that's copying a creature, they will become whatever the chosen creature is copying.

You choose how many targets each spell with a strive ability has and what those targets are as you cast it. It's legal to cast such a spell with no targets, although this is rarely a good idea. You can't choose the same target more than once for a single strive spell.

Effects that have already applied to the target creatures will continue to apply to them. For example, if Giant Growth had given one of those creatures +3/+3 earlier in the turn, then Polymorphous Rush makes it a copy of Pensive Minotaur (a 2/3 creature), it will become a 5/6 Pensive Minotaur.

The target creatures copy the printed values of the chosen creature, plus any copy effects that have been applied to it. They won't copy counters on that creature or effects that have changed the creature's power, toughness, types, color, or so on.

If such a spell is copied, and the effect that copies the spell allows a player to choose new targets for the copy, the number of targets can't be changed. The player may change any number of the targets, including all of them or none of them. If, for one of the targets, the player can't choose a new legal target, then it remains unchanged (even if the current target is illegal).