Free will: an illusion

You're making a common mistake.It is correct to say that foreknowledge doesn't (necessarily) constrain the future (it might, but there need not be a causal link). But it's wrong to say that foreknowledge is compatible with a future that is not constrained. Foreknowledge is only possible if the future is fixed (at least to the extent that what is foreseen MUST happen)..

If there are multiple possible outcomes and God knows all of them then God can't meaningfully predict the future other than to say "one of these several things will happen...". And if God actually sends a prophecy that one of those things will happen it will often turn out to be wrong (if you hold to the idea of multiple timelines it will inevitably be wrong in some of them)So really that isn't what we would think of as the full foreknowledge attributed to God in the Bible.