Who I have the same questioned this topic

My daughter was given a new Galaxy S4 about a year ago from a now ex-boyfriend. She has a Verizon plan but wanted to upgrade to an  iPhone and couldn't find out where he got the phone and now it is too late to return it. It is sealed in box but boyfriend told her that it was Verizon compatible a year ago when they were still speaking. How can I tell if it will work? Will I need a new SIM card?