Chances are an older stepping will be recognised in a newer BIOS version.
My Mobo came with BIOS v1.10 and even the newer v1.20 still does not support the i5-3450T as per CPU support chart.
But I'm happliy watching TV on the highly improvised HTPC with the i5-3450T, the BIOS recognises it as the correct CPU, CPUz reports everything that's it's supposed to support is enabled.
A BIOS would have to exclude a certain stepping for it not to work.
All OEMs get ES samples to make their BIOS's from and Intel send the stepping/microcode listings to the OEMs.
It would be very unlikely that a CPU would not work, unlikely but still possible.
It could very well be that certain things may not work on the CPU.
It's all a risk, I've yet to be stung, but one day I might, but do you homework, let Google be your friend.