Can prayer change God's perfect plan?

[FatAndFaithless]

You can't say that we have free will if we "can't help" but act according to his design.  That's what a puppet does.

I agree with this. And for the record, I don't see it in the way that other poster does.

As I explained, God knows what we will choose in the future specifically because He is not bound by past, present, and future. He can see everything happening all at once, like looking at a timeline of the beginning of time all the way until the end of it. This does not mean He controls what we choose, it just means He is already seeing what we will choose because He is looking at all of time from the outside of it.

But of course this gets to the point where that's what you're asserting what God's nature is, and actually demonstrating this assertion is another ball of wax entirely.