just to let you know how I went forward i hope it will help some one in future ,
e84 with working dme and key dead cas
Since i did not have a donor cas with working key. I borrowed a car with same specs made a key in key position 7 , read this cas eprom and flash (with vvdi prog) wrote it on the dead cas and changed the vin in the cas using the advance option (cas replacement) and then read the dme isn and wrote it to the cas
It worked
thank you all for you input hope this helps someone