Activation lock

You acquired your device second hand from someone other than Apple or an authorized Apple reseller. The information below explain what has happened. You apparently didn't know to heed the advice given below.

"Before you buy/acquire an iPhone, iPad, or iPod touch from someone other than Apple or an authorized Apple reseller, make sure that the device is erased and no longer linked to the previous owner’s account."

And see: Activation Lock for iPhone, iPad, and iPodtouch  https://support.apple.com/en-us/HT201365. See this heading Check for Activation Lock before you buy/acquire a device from someone else.

 What all this means is that there is no way we can help you. We are not authorized to remove the

activation lock from any device. And, under your circumstances, Apple support will not help you since you cannot provide proof of ownership that they will consider to be sufficient. You would need and have your purchase

receipt for the device from an authorized Apple seller with the device's serial number on it. 

Usually, I would suggest that you try to recovery the needed password from the party you acquired the iPhone from. But, I see that this party couldn't remember the password. I emphasize that recovering the password is the only way the phone can be made functional for your use or sale. And getting it from the person you acquired it from is the only way to so.

No. That previous owner will have to recover their AppleID and release the device. Apple won’t get involved in any issue with a second hand sale of personal property.

Tell the owner to try and recover their password here -> If you forgot your Apple ID password - Apple Support

Once they have reset the password, they can release activation lock using the instructions here -> Turn off Activation Lock - Apple Support

See If you forgot the answers to your Apple ID security questions https://support.apple.com/en-us/HT201485

You indicate hat you can't answer your security question satisfactorily. So see Security and your Apple ID https://support.apple.com/en-us/HT201303

This document says “without proof of your identity via security questions and other carefully selected criteria, Apple Support can't help you reset a password or perform any other actions on your account.”

Thus, given Apple's notification, we can do nothing to help you, except to mention that Apple support might help you if you have an extenuating circumstance (e.g., you have your receipt for your purchase of a pertinent device from an authorized Apple seller with its serial number on it). If you want to contact Apple Support to discuss any possible extenuating circumstance, see the support options below. Alternatively, if an Apple Store is open in your area, then you can go there to deal with your extenuating circumstance. You also can make a genius-bar appointment (https://www.apple.com/retail/geniusbar/) if you want.

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option.

You can try. See the Apple Support articles below for contact information.  

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.   (Link doesn’t always load)  

Get Support          Work through the screens to get a chat option. 

Apple Support schedule phone call

https://twitter.com/AppleSupport

Normally, Apple requires a copy of the original purchase receipt with the serial number on it.

No, as explained above, Apple will not.

You are welcome. Glad to help.