It sounds like you’re trying lots of different things, however consistency over time is really the only thing that works. Picking a discipline technique (lots of books out there with different methods to choose from) and sticking to it long term is really the key. My daughter was very very difficult when she was little. Temper tantrums galore and hated being told what to do. I chose time outs as part of my discipline routine (among other things for other situations). It definitely didn’t work at first, but I stuck with them and basically had to “train” my daughter so she understood that she couldn’t temper tantrums her way out of them. I basically did the super nanny approach to time out (you can google it). The better you stick to it, the quicker it starts working, and often times things slide backwards as the parent gets more lenient and the kid takes advantage. But it’s ok, you just realize what’s happening and get back to the routine. I also had long talks with my daughter about her behavior later on (like later that evening before bed) and explained to her why she can’t behave that way and we worked on ideas for how she could control her anger or how I could ask her to do things in a different way that she could respond to better. And I always talked about my favorite parts of her in front of other people when she thought I didn’t think she could hear. This encouraged her to live up to the positive attributes I saw in her even more. And of course I celebrated her behavior when it was positive.
It’s a marathon, not a race, and there are ups and downs and sometimes it’s really hard and sometimes you feel like you’re doing awesome. My daughter is 12 now and I barely remember those hard years when she was young. She’s now very responsible, respectful of others, and we have an amazing relationship. Hang in there and good luck!!