This question is an exact duplicate of:
I bought icloud-locked iPad which was stolen from trash center in Denmark. Honestly, I did not know they were stolen and I was scammed. (The seller did not even say they are iCloud locked)
I jailbreaked it and removed Accounts the sqlite database. It did remove locally old apple ID, but not on apple servers. (i have been told, but logically it could not remove it from apple servers)
It then was this login form as if i had logged out normally, I logged in, it was like 2min waiting (seemed a bit too much, like it would not work), but surprisingly it worked and I can see the iPad on my find my ipad page. Localization services are disabled so I cant track its location though.
But since Activation Lock is gained from remote Apple servers (or local account data?) what would happen when i would reset the ipad? I do not want it as i do not want to get activation lock for the old account I do not know the password for.