Installed Mod Bios By mistake, Serial Number change

Hello there,
I have a Lenovo U310 Ideapad system, I updated my bios from 65CN21WW to 65CN99WW from Lenovo website. After the update, my system became slower and I started having serious issues with Intel rapid storage. So I wanted to revert back to the previous bios but Lenovo doesn't allow that. I spend days searching the internet without help of how to revert back.

Few days ago I was thinking of changing my wifi card, but Lenovo has a whitlist, so I went to the forums to read about it and I found an already uploaded 65CN21WW with whitleist removed, so I flashed it and it overwritten the 65CN99WW bios(I didn't know that this can change my machine information). This fixed my issues with the slow system/rapid storage, but after the flash my Windows 8 needed activation again and it seems as if I lost my product key. I went to the bios and found that the serial number there is different from the one printed on the back of the laptop.

So can I get my original serial number UIUD back to original? I have a backup of the 65CN99WW bios (before flashing). Is there a way to have 65CN21WW but with computer info from the 65CN99WW backup so that Windows works again?

Thanks