imei info with baseband

hi i have a few questions

where is the imei information located in iphone

is it in the hynix nand 16gb harddisk or in the baseband possessor ?

also if i have a iphone that i replace the baseband chip on will it change the imei on a iphone 6 ? or unblacklist it ?

i have a iphone 6 that was balcklisted due to nonpayment of bill ?

is there any programming involved with the baseband if its stored on the baseband or when i buy a new chip does the new one already have a new imei

and or do i change it in the harddisk nand with a 64bit nand reader and will it have problems activating if i change the imei ?