If it's working with that then it's unlocked from the Sprint network now and any sim can work in it.
Yes it won't be a problem. Just go ahead and do your factory reset now.
Ok, wil try later factory reset.
Btw, mobile data is not working. APN setting is not accessible. Could you please advise what should I do to enable mobile data service?
The mobile data would be enabled when you have service on the phone. Do you have services turned on with a carrier?