Assume that the future can change based on your actions, so any historical information that you bring along with you from the intervening 25 years may quickly drift out of the new realities history.
Edit: also assume that you can be given a healthy 21-year-old body if you want or take your previous self’s place.
Further, identification will be provided for you if you were not born at that time.
That’s a good idea but I wonder if anyone would buy them? Obviously the technology inside of it would be a quantum leap for any tech company that could get their hands on it. AT&t or ma Bell or Motorola would all easily fall over themselves to hand you several million dollars for it just so that they could have their top researchers reverse analyze the equipment.
The downside to that issue though is that it would be very difficult to get in contact with the right people to sell these devices at the right price.
That kind of technology is hard to get any value from. Nothing in modern phones is innovative, and most of it would be an obvious evolutionary step to any specialist in their field.
Mostly, though, the phones would be useless. Cellular networks were in their infacy, and none of the standards or technology existed to charge them. Reverse engineering anything in them would be hugely expensive, for little return.
Smart phones would be interesting, but far less interesting than the existance of a person who has access to future technology. I think op would dissappear into a government facility not long after trying to pawn their goods.