Reset iPhone identification

Just bought this phone from little nephew and it’s with sprint(unlocked for all carriers) and using it now. Wondering what services are available to make my phone different from how he had it after I’ve factory reset it. I’m just getting used to the cloud and other internet protocols and identifiers so I’m looking for the resources available to change Phones IP address and even all the way down to the iphones imei just for more security. Please respond and help me soon