The replacement devices start with an N instead of an M.
MN5T2LL/A is a Verizon 128GB Black iPhone 7+. If it is a replacement device, it will be the same number but start with an N instead of an M.
It should be. But I can tell you with the iPhone 6, I received a replacement device that was locked to Verizon. It was a PITA to get it unlocked.
Buy the GSX report from ebay for 99 cents and it will tell you the lock/unlock status of the replacement device.