Activation Lock

If this is a used device, you will need to contact the previous owner to have them log out of iCloud or go to iCloud.com/Find My Phone and erase the device, then remove it from their account. If you can’t do that, the device is useless. 

Activation Lock - Turn off Find My iPhone 

If necessary, if you are the original owner, take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store.

Genius Bar Reservation US

or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.

Apple ID Support

Apple ID Support (2) 

Apple Support by e-mail or chat         

Apple Support using Twitter

Or fill out and submit this form.

As I posted above.

or contact Apple ID Support. They will need to see the original purchase receipt/paperwork also.

Apple ID Support

Apple ID Support (2) 

Apple Support by e-mail or chat         

Apple Support using Twitter

Or fill out and submit this form.

Is this a used iPad? If so, it may be locked to the previous owner's Apple ID.

You may need to have Apple unlock it, as I posted above.

Does the Apple ID work to sign in other places?

For your password question, you can try that. See the Apple Support article(s) below.

 Apple ID Password Change

 What to do after you change your Apple ID or password - Apple Support     I suggest doing this before you change your Apple ID or password.