Yes, the law does protect the picture. You own the copyright from the very moment the new work exists.
You may decide not to protect your copyright, but it is yours to do with as you please.
It's kind of like that and kind of different. The copyright exists from the creation of the work; the patent does not exist until it is granted. Copyright offices merely register claims. Patent offices determine whether the claims are accurate.
Probably not--but only because there just isn't enough money in model aircraft.
But if you copy the trim scheme of a NASCAR driver on diecast models, you'd better have a whole slew of contracts in place to protect yourself from copyright and trademark infringement. There is definitely enough money involved in diecasts to make prosecution worthwhile.
They do if the author or the author's heirs do not renew the copyright. Off the top of my head, the initial copyright is good for about 75 years nowadays before it needs to be renewed.
There isn't any software that's more than 75 years old. Any software that truly has become "public domain" has done so because the owners of the copyright decided to make it so. It can't happen by accident.
Marty