If your Nokia 1202 has a corrupted IMEI (e.g., “IMEI invalid” or “00000000000000”), the only legitimate path is to use to reflash the original backup RPL file from that specific phone — not to generate a new number.
In many countries, mere possession of IMEI-changing tools with intent to use them on a phone you do not own is a felony. Always operate within the law. nokia 1202 imei change code