Does free will exist? You can't act differently, but only because you are you. You're not some standard human who will always make the same choices given your body.
I see a tendency towards disassociation here. Your identity includes your body. No, you can't entirely choose your identity, but if you accept that is who you are, then your choices are wholly your own.
There's no time gap where you could choose an alternative. And you can't choose your environment. But you aren't abstract from it, either. You know you make choices. They may not be "free," per se, but they are personal, and the personal is real.
So maybe not "free" will...we are constrained...but personal will is real.