What problem(s) you are trying to solve? You got a new phone from the service centre, of course the IMEI is different.
You can back up GDFS of your phone to your PC. A different phone will have a different GDFS file created by the backup.
You should always back up GDFSt to the PC before flashing your phone.
I guess you only flashed the MAIN but not the FS of your phone. So you now have a phone that has mis-matched firmware. That's why you see 'both R6BC002 in the first line then rolling down i see the same R8BE001'. This may or may not cause problems in the future, but the MAIN and FS should be of the same version whenever you flash the phone.
You should either
1. flash R8BE001 MAIN to make everything R8BE001
or
2. flash R6BC002 FS , then a proper custpack or perform finalization using XS++, to make everything R6BC002