Can you use an iPhone with a USA sim card abroad?

SO I found two pretty cheap iphone 5's on ebay. One is locked to Sprint and the other is locked to AT&AT… Now in the AT&AT one there's the sim card verification error.

If I were to buy a Nano Sim for Activation Screen Bypass Only would I be able to freely use my iPhone in Ireland?(I'm not interested in making calls and texts for now I would just like to try the phone out)

Oh and also could anyone explain what this means? I'm not very techy:
FOR PARTS ONLY - AS IS

ABSOLUTELY NO RETURNS.

WON't RESTORE WITH ITUNES.

Please VIEW ACTUAL PICTURES.

iCLOUD IS DISABLED AND THE ESN IS CLEAN. THE MOISTURE STICKERS ARE WHITE.

Anyway thanks… Please don't tell me to get an android phone or anything like that because I have one… Just answer my question please.

Att store should be able to answer all your questions

I have friends that do it in India with their iphones, but it needs to be unlocked