Yes, rear door open, measured to ground. But eyeballing from the tape measure to the seat top.
#3 there is a shade cover from behind the seat backs (when up) to the tailgate. It is removable, whether the seats are up or down.
#2 there is a 4 point (adjustable) cargo net in the convenience package- but it extends across the width of the back, so if there is stuff under it it will be secured from sliding I to your dog, but if your dog decided to shred it ..
#1 I cover the backs of the seats, door panels etc with a beach towel. Dont know if alfa has anything special, but no doubt any upholstery shop could make you whatever you want.
Between the seats splitting and folding, and the net, and a bit of thought depending on day trip or long trip, how much stuff etc, it's going to be way easier than sticking a big dog in a bag in a giulia.
Our dog is small, but I've had big ones that got old. When it gets to the point where you are picking them up to put them in and out, and they want to lay down, you'll appreciate the hatch more.
Although if you are camping etc youll really appreciate the easier loading anyway.
Edit - if you haul a lot of stuff, with the roof rails you could do a Romney haha