My phone GT-I9000 shows baseband unknown and IMEI is empty after I had upgrade firmware.I don't have efs backup. Some can help me? Please.
check under battery for IMEI number and check it here
once you are sure what model you have, than a solution is feasible. read [Tutorial] How to Unbrick, Flash, Downgrade, Root, Update i9000 from Froyo to Kit Kat