All non-LTE communication relies on the ESN number only. If Verizon doesn't assign a Verizon ESN number to a device and/or refuses to activate whatever ESN the device may already have then you're out of luck. You want Verizon to give you an ESN they'll agree to activate and you're not Apple? Make sure the word "Verizon" is physically printed on the phone, make sure you include a bunch of bloatware, don't ever try releasing software updates because we'll delay them by months, etc.. etc...

You don't have to deal with this kind of nonsense with GSM carriers so long as you have an unlocked phone you're good to go.

They use LTE sim cards. You still need CDMA to make calls and send texts.