First, was it abandoned or were the residents fleeing for their lives under duress? Yeah the latter. This is very far from being long abandoned property. Even if the owner was killed, it's not a sudden finders keepers. There are wills, or even without a will there are still legal inheritors that the courts figure out. Again, this is not an event from long ago, it literally just happened. If you want to claim legal ownership rights over something that wasn't yours to begin with, it's a serious task and the burden is on you. You don't automatically assume legal ownership, basically the court would have to find in your favor that you can claim salvage. Until and unless that happens, you don't have legal ownership. That means any difficulty/ambiguity/complexity in the matter leans away from the courts giving you legal ownership. Also, generally as the value of the object goes up, the difficulty of the salvage ownership claim goes up. The value and complexity of a working android is unfathomable and the difficulty of your salvage claim just shot into the stratosphere.

Second enlistment. This is not about learning. Enlisting is a contract. You need to have agency to sign that contract. This is why people under 18 and feeble minded people can not enter into a contract - they do not have agency.

That's what Picard should have argued: 1) The very act of Starfleet accepting Data's signature shows they thought Data had agency. Precedent was set. That means both sentience and the ability to decide to resign. That alone basically wins the case. But failing that we can look at the other side: 2) If the judge says that he has no agency to resign from Starfleet, that means that Data never had agency to enlist in Starfleet in the first place. The entire contract is null and void. Data has no legal relationship with Starfleet, they can not give him orders to report to Maddox, and Data is free to go. Which leaves you with the salvage claim, and as above good luck with that you're going to need it.

That's basically the same as what I said before but with more elaboration. That's as elaborate an explanation that I care to make so I think that's my last reply.