[dstaley]

You still need some sort of authentication before the vehicle will let you switch into drive. In a Model 3, those options are either an authenticated smartphone, a key card, or a key fob. You cannot enroll any of those three keys without having an authenticated key present.

[mehrdada]

I do not believe this is true. You can start the car with just the account credentials. You will have two minutes to start driving, as the GP states; it’s called keyless driving mode. I’m pretty sure as I have used it when my phone broke and started the car with unpaired iPad. You need a key fob or key card to add a new paired key/phone, a paired smartphone doesn't work for that.