IP Modal Number

hi good day! Just a little bit confuse about modal number on iPhone, if it starts with M means that the iphone is new right? if it starts with N means replaced iphone (is this model good or worth it to buy?) if it starts with F means the iphone was refurbrished and if it starts with P means that the iphone was is personalized. Am I correct? So, I just wondering if the capital of modal number on iphone starts with N, is a good quality/worth it to buy or not?