So it seems you flashed the complete SG/MY firmware did you? If so you've changed the HWID to 0930.

What RAR file did you unpack to SD? Supply a link to it please.

"When I plug in my PC, it restarts and the white screen flashes up" I don't know if you mean it does that trying to connect to PC in (i) Mass Storage Mode, or (ii) preboot or (iii) both. If it's to be recovered it must at least be able to enter preboot. Can it?

Answer all those questions above please and also give any other info likely to be relevant. If you want help with this it's essential to know exactly what's been done and how it's now behaving.