I took in over 300 baby kittens when I had my rescue. Bottle fed them all. AT 12 weeks they are already imprinted to fear if the kitty was outside and probably with its mother for a while. I would personally skip the collars and such. Patience is absolutely the key. My Meowie is about 6 yrs old. She was a stray my son had picked up about three months old at the time. She is selective in her humans now. Two years of living here before she let me pet her. She choses when and she is not a lap cat. she sits on the arm of the couch. She hated my other pets for the longest time hissing and running. now she is the queen of the house. no one messes with her. she plays when she choses then she sits back and lets them know enough. So patience has its rewards.
Immediately: crate then leave the crate in a safe room opened, silent no dogs no noise you can sit on a chair with a book or something let the cat decide when it wants to come out and explore. leave the crate open it will chose to go back there especially if its where food and water and a good place to hide if it needs to. It has to feel safe to explore. soon it will know you are the giver of food. and wait for you to feed it. eventually you can pet the kitty just dont force it. let the cat know you. talk softly, speak its name.. its young you will be fine trust the cat and trust yourself to be patient. Probably not a lap cat but maybe a good companion anyways? mine likes to put her paws on my leg when I sew and has this tiny meow.. ok pet me now. argh. i do
anyone who will tap my leg for a rub gets a rub. so cute.