I have an iPhone 4s. Recently I upgraded firmware of this phone and then I can't active iCloud activation and can't use my phone. Cause, I have totally forgot my apple ID, password and all related things. But I have IMEI and Serial number and other information of this phone. How can I do now to recover it or use new apple ID?
iPhone 4S, iOS 9.3.5, Serial No: C39GJNR7DTDD
Are you the original owner of the iPhone? If not, only the previous owner can remove the activation lock:
Turn off Find My iPhone Activation Lock - Apple Support
If you are the original owner and still have a proof of purchase, Apple may be able to reset the device for you. I suggest the quickest way is to make an appointment at a Genius bar in an Apple Store near you and take the documentation. You may also be able to this online. Either way:
iCloud activation problem
