[Dimensio]

Actually, by prefacing the premises with "only Y, if Y exists, can do X", then it does logically follow that Y does exist if X is done. It isn't affirmation of the consequent because it is stated beforehand that the consequences will occur only under the condition that the premise is true. It's a difference between "if X then Y" and "if and only if X then Y".

[general_re]

Actually, by prefacing the premises with "only Y, if Y exists, can do X", then it does logically follow that Y does exist if X is done.

It's equivalent to rewriting the premise as such:

P1. If God exists, then only God can raise people from the dead.
P2. People have been raised from the dead.
C1. Therefore, God exists.

And this is affirming the consequent of the conditional statement in P1, not the antecedent. Keep in mind that the ultimate conclusion is supposed to be that God exists.

It's identical in form to the following syllogism:

P1. Only general_re, if general_re can fly, can stand on the roof of his house.
P2. General_re can stand on the roof of his house.
C1. Therefore, general_re can fly.

The flaws of such an argument are obvious ;)