How to activate iphone 4 ?

hello everyone, i am using iphone first time and took the iphone of my uncle, when he registered the phone he used his apple ID ... now gave to me, i have my own apple ID(iCloud) and wanted to change it under my account, from settings i tried to change but it offeres only to delete the current account before creating new one. So i tried, but it asks for password which we dont know, my uncle forgot the passward of his Apple ID as well. There is no way we can reset the passward and there is no way we can delete the account sisnce we dont know the password (which is un resetable)😕.

So i thought that i could reset all the data in the phone into its factory condition if i try put password on phone and enter it wrong 10 times. it worked the phone is reset to factory condition but when i tried to relounch it, for activation it is asking to put the same apple ID and password as my uncle used when he was activating the phone... i am very 😠 cause now i cant even use the phone....it doesnt offer to use new apple ID to activate the phone, i dont know how to register new Apple ID and i dont know how to activate the old one cause have no access to old apple mail.

One more time, the problem is in iCloud mail ID.

Also he used this action "find my phone" or something like that.... have no idea what does it mean! 😕

ANY sugestions what should i do? please HEEEELP ⚠ S.O.S ⚠