iphone8
Can you do find my iPhone on a device not activated or find my iPhone is not set up, but you have the serial number plus the Apple ID
iPhone 8 Plus, 12
Question marked as
No.
Apple - Find My iPhone, iPad, Mac, and Apple Watch - http://www.apple.com/icloud/find-my-iphone.html and: iiCloud: What is Find My iPhone? [formerly: Cloud: Find My iPhone overview] - http://support.apple.com/kb/PH2696
The following conditions ALL have to be met:
1) You have the "Find My" activated BEFORE you lose the device.
2) The device is turned on and for cellular connection has a SIM card installed.
3) The device is able to connect to a registered wifi connection (iPad, iPhone, iPod Touch, Mac) or data network (iPhone, iPad with cellular).
4) The device was not restored by a finder of the device (if it was really stolen then the thief has probably restored it unless activation lock is active).
iCloud: Locate your device with Find My iPhone - "If Find My iPhone can’t locate the device, the last known location is displayed for up to 24 hours. " Lost Mode.
https://support.apple.com/kb/PH2698