Difference between IMEI, IMSI, ICCID and MSISDN numbers

Why there are 2 IMEI numbers in the phone? imei slot 1 and 2 Looking at the imei parameters I noticed that the imei sv is: unknown, slot 2 nano sim imei sv: 01 works very installed a imei slot 1 or 2 Once two imei exists such phones carrying it will be blacklisted and will seize to function; this happens on tech errors Yes, people swap imei

imei slot 1 Card Slot 1 nano SIM + 1 nano SIM micro SD More Standby Mode Dual SIM Dual Front f , Rear f + f More Flash Rear