Re: I just realized I have no idea what I'm doing.
When I brought Zenobi (senior -- elevenish) home she made straight for the litterbox. As I had decided to give her as much freedom as possible, I opened most of the doors. Two closets, the second bedroom, the basement to allow her to explore 'her home'. There were a couple of problems due to her past experiences. She was always terrified after she'd used the litterbox. I finally decided that she'd been punished at some time for spreading litter -- which she's quite good at -- and I spoke calmly to her in the spot she'd chosen as the best place to hide. When that didn't help, I started to just clean the litterbox and say nothing. That seems to have worked quite well, although after eight month she still has anxiety days. Food was another problem. She wouldn't touch the good stuff I bought. I managed to get her to eat tuna, and then tried her with the Whiskas dried that I'd been feeding to the recently killed feral. That was good. The only problem was that she started throwing it up as undigested tuna and kibble. This is where reading this forum came in handy as someone mentioned that tuna was bad for them. I stopped that and the kibble stayed down. After more experimentation I settled on the Whiskas kibble (salmon flavour is her favourite) and Friskies salmon dinner,she won't touch the other flavours). I would have given her the best, but I suspect she doesn't like the turkey that is used for a lot of the protein. (That's not true for the cat that sometimes turns up looking for nosh, as it did today. I gave it some of the 'better' kibble that Zenobi won't touch.)
The thing is, that cats are individuals; somewhat like humans in that regard, and what suits one does not suit the other.
The other big problem that I had was her biting me for what seemed like no good reason. Three times, but one was when she mistook my thumb for a cat toy. Then, thinking about it, I relalised that she did it when she saw a petting hand approaching from the wrong angle. Pure supposition, but I think she may have often been grabbed by the scruff of the neck and beaten. I gave her a lecture about biting with repeat demos as to what was not good by pretending to bite my own arm and pointing to her. "You bit me." Eventually she hung her head and turned away. She's only bitten me once since then, and I think that was an unthinking reaction. She did hang her head that time as well. Now I watch where my hands are. I rarely pick her up, and then never to pet her. I never hold her against her will. I try to treat her as I'd want to be treated if I were a cat.
I know some of the above goes against the general advice given on this site, but it's worked well for the two of us.
When I chose her, by the way, I did so because she looked terribly depressed in her cage. I had intended to foster a cat first, but when I saw her condition, I gave up that idea.
I don't suppose I'd be able to be as permissive if I had more than one cat, or if I didn't live alone. Still I thought I'd lay out my experience in case it there would be a time when it came in handy.
By the way, she gave up the nightly closet inspection that she'd been doing. She does come to see me first thing in the morning and she loves to make sure I'm safe in bed at night, although she might be coming to watch the strange routine of the changing of skin that takes place.