Are newer iPhones unlocked by default?

I have a few iPhones which were either provided by Verizon Wireless or Assurion as replacements. I have since replaced all damaged or lost phones as I'm leaving Verizon Wireless this month and will no longer have coverage with Assurion.

As far as I know, iPhone 5 and higher are unlocked, as well as newer iPads. Now I'm not sure if this is per the carrier (Verizon Wireless in this case) or is this just an Apple feature on these devices?

It appears that there's not much of a carrier validation when you Bring Your Own Device to a carrier, I've switched SIM's between a few carriers/phones and the phone almost instantly works. With that being said, it doesn't appear that there's a way for a newer iPhone to be black listed if it's unlocked, is that correct?

The reason for my concern is that one of my ex-friends on my family plan was unwilling to pay their share or continue to make payments for the device or return it. I've reported it to Assurion but I'm wondering what would happen to the device reported.

Its sounds like Assurion can only deactive the device via Verizon not through smaller carriers who allow for bringing your own device, is that correct?

Added (1). I think it was clearly stated but let me clarify, all the iPhones I have are unlocked and have already been moved to another carrier while in contract and all have clean IMEI but I'm inquiring about the one reported stolen, will this person likely be able to move to another carrier or is the IMEI black listed on all carriers?

Added (2). Is anyone actually reading the question?

It's confirmed that these devices are already unlocked…

I don't need to check… The question is if the device that is reported stole, it is also unlocked by the carrier - So how will this affect the device? Will it be blacklisted on all carriers, will it be banned from Verizon Wireless only… What?

No. Unless specified they are unlocked they are locked to a carrier. If you got them from a carrier or through a carrier they are locked to that carrier. And only the carrier can properly unlock a phone.

Carrier based iPhones and iPads are still locked when activated. SIM or not. It's just that Apple makes more unlocked models available via them and others sellers than they ever used to. They have to lock in order to protect their investment on a financed contracted device. Based on your story, friend's said phone still under contract will in fact be blacklisted on your plan. I'm not sure how Assurion being insurance would have anything to do with it unless you are reporting it stolen by the individual. True that Big Red, ATT and very willing to unlock devices once contract is complete. Sprint continues not to do so BUT they will by early next year according to FCC and CTIA agreement.
http://appleinsider.com/articles/13/12/12/us-carriers-agree-to-standard-set-of-rules-for-unlocking-phones-tablets

Depends on the carrier, if you want unlocked then you just need to check to make sure you are buying the phone outright and that it is not locked to any carrier.

No, but you can buy an unlocked version or unlock it yourself. If you're unlocking it yourself I recommend ChronicUnlocks.

Any phone you bought through a carrier at a price other than the full retail price will be locked, as the carrier wants you to pay for your contract until the cost of the phone is amortized.

A phone bought from a carrier for full price may or may not be locked.

A phone bought directly from the Apple Store without a cell subscription will always be fully unlocked. Of course, you'll have to pay the full retail price for it.