Okay, I fixed the inverted screen myself following the second half of carloswii5's guide. It was painful to navigate with an inverted screen but it can be done. You must flash stock 10G, enable USB debugging, root 10G, install CWM recovery, and then run some shell commands on your computer. For what to do, start from step 6 of the guide here
. However, when flashing stock 10G, set the PhoneMode in UpTestEX_mod2_marwin.exe to Emergency. Also, you don't need to do step 7 of his guide if you failed to unlock the bootloader.