Can I use a SIM card from one phone to activate another? (iPhone 4)

I have two iPhone 4's. I forgot the passcode to one of them so I set it to restore, but it's requesting a SIM card. I have one in my other phone, is it okay for me to use that same SIM card to activate the second phone (even if I eject it again after restarting the phone). It's been connected to Wi-fi, does that mean I don't need a SIM card? I don't know if it's a GSM or a CDMA, but the model number is A1332 if that helps... I've been trying to fix this for months, please help!