There will be a Signature version. How many will be the question. I expect a lot more than the Model S and Model X.
I definitely expect two versions of the battery pack and how much kWh in the big one is going to be interesting. I'd assume as much as they can mange to fit in the space available. The base level will be what everyone else has said: 45 to 55 kWh for a minimum of 200 realistic miles.
4 door sedan hatchback, like the Model S.
Acceleration better than a 2018 BMW 3 series base model. I'd guess less than 6 seconds 0-60. The instant torque will blow away most consumer's expectations for quickness.
No automatic door handles. Maybe on a loaded model.
I will guess that reservations are more than 200,000 by the time production begins. $5K for Sig and $1K or $2K for general production. It will benefit Tesla to have an enormous reservation number since they will likely need some more loans to cover infrastructure build out for the Model 3.
I suspect the door handles on the Model 3 will be hot spot handles like on the Model X without the auto door opening mechanism. Those hot spot door handles can be done very cheap and have no added drag.