when u reflash a new KV to a banned jtag do you use the new CPU key and DVD key or the ones that the jtag started with

also can i pull the KV of of an rrod xbox without needing xell bc i have 4 rrods and they are all exploitable but i cant get any of them to boot not even for 5 sec one tried heatgun and xclamps 2 have bad ram 1 has gpu error and the other is a mosfet problem. thanks for the help