I think this is the terrible 2's definitely. You can try some sort for different discipline if what you have been trying isn't working for you. I have had children even up to 4 who will just ignore me and do what I told them not to, pretend not to hear me, just be wild and run around everywhere in the house. None of them have a disorder.
You should try giving him a little more attention and provide him with some sort of good outlet for his excess energy. It's normal for kids this age to be practically bouncing off the walls, especially when it's too cold to go outside. Let him get out his energy...except you must not tolerate the hitting...make sure you are adamant to him that that is NOT acceptable.
Even if it is cold, you can take him outside for 15 minutes and let him run as much as he wants. The fresh air is good for him and he won't feel cooped up and trapped....I can tell you right now, my kids are horrid when they haven't been outside for a while.
If he ignores you and does what you don't want him to, you need to be consistent and act on it every time he does it. My children are put in a chair in the living room and must sit and be quiet for a time. I don't think this will work for a 2 year old, but there must be some sort of negative feedback that you can give him that will respond to his negative actions....you could also have him lie down in his bed. Sometimes he might be over tired....which also causes hyperactivity.
A little change in his diet may also help. Limit his sugar intake drastically if not altogether. You will find a marked change.
You can try a positive approach, but this usually doesn't work in children who are so small, unless you can keep it very short term, since children's attention spans are naturally less than 5 minutes.
