I was given a used ZTE Z835 smart phone with no sim card...

I was given a used ZTE Z835 smart phone with no SIM card several months ago. The owner (visiting a friend at the time) said they didn't need it (got a new iPhone). He said to just buy a SIM card and it would be OK. There was no cord or other parts, so I found a cord and charger and it charged properly. When powered up the AT&T blue globe was shown and I gave the initial swipe. It came to a number pad screen and requested a sign-in pattern. There was a note about the last sign-in being over a year ago. No name or details otherwise. I found the instrux to reset the phone by a side button sequence and did so.

After this it will start and ask if I want to copy data or set up as new. I pressed set up as new. Now it wants to verify my Google account to sync with. I have no such account (and I do NOT trust Google with anything). It will not get past this point to do any other function that I know of. I set it aside til today when I had time to futz with it again. So...

1. Do I just buy a SIM card and get going or is this phone still chained to the long gone owner?

2. Can I divorce from any Google accounts?

3. I'm disabled and hope to use this phone on the Lifeline government access program I found. AT&T Lifeline provides a discount.

4. Is the phone unlockable? I've found there are completely free Lifeline options with several services (some are even AT&T connected).