If it can, then how? If not, then how come?

Looking to hear from people who think (or know ) they know what they're talking about. I'm having trouble understanding the more general idea. Like, if it's even possible, then is it permanent, or would you revert back after a while?

This is of interest to me because, due to various factors I can't really ignore, I don't feel like I know who I am anymore. I'm not even 100% sure of my type, IEI just seems likely and is the result I get most frequently. I relate more or less to most of the type descriptions on some level, and re-reading them to pick out what's conditional and what's always been true feels impossible and truly headache-inducing. I'm also interested in understanding if/how/why type can change so I can understand my friends' behavior better.