I flashed an incompatible ROM on my S3 and it no longer booted. thankfully there are dudes on eBay who can fix them for about 30$US. you send them your phone and they hook it up to a specialized program called Riff box and connect wires to the Jtag terminals on the S3 main board. it works! so don’t give up, OK? I can vouch for one guy. I’ll dig up his info later. only sketchy part is maybe they clone all your info but you don’t have any other options except buying riff box yourself and it isn’t cheap.