Sorry I had forgotten about my post here. I am unable to post photos rn since I won't be home for a bit but I can describe stuff.
There are no serial numbers, markings, or dates. Function wise it is the same mostly. Your pet dies super easily and only evolves once. Marriage happens quite soon. When you restart the device all potential pet sprites flash across the screen. They are all sprites stolen from different franchises. From what it shown I recognized Digimon. There might have been a stolen Tamagotchi sprite as well but I do not remember for sure. Most of them I could not recognize.