Their meanings are all depending on the context . For example, 没用=没有用 1) as an adj,,, it means something is useless or somebody is incompetent / not productive in a team 2) as a negative term of a verb, it means " I didn't use it / I haven't used it" -------How do you like the shampoo we bought the other day ? -------Oh, I haven't used it yet . <我还没用。> AS for 不用了 , when someone's trying to help you or do something for you, and you don't need, you could anser "不用了", meaning "don't bother, I don't need it. " When it refers to something you used to use, but don't wanna use it anymore, you could say "我不用了”，meaning "I don't use it anymore."

不用了 = I'm not going to use it. = I don't need it. 没用 = 没有用 = I didn't use it. And yes, 没用 = 没有用

Always it means： 不用了=I used to use something,but I will not use it. something is 没用（的）= useless =没有用（的） In communication： If you gave advice to smoebody,then he says 不用了，It means "thank you all the same." And when he says 没用or没有用，then your advice is useless.

不用了：用不着,不必了（它可能有用，但目前暂时对你没有用。）不为所用；不应用；不听从； 不采纳；废弃 need not 没用： 无用。1.不起作用；没有用处；2.以指没有作用的事物。3.不需要；不用。 4.犹无能；没有才干。 useless; of no use; of no help 没用：否定的意思 没有用：不完全否定

Simply, Q1. What is the difference between 不用了and 没用? ——不用了 as a phrase means 不需要了、不必了，it's more polite. ——没用 as a phrase = 没有使用 e.g. 这部电脑没用杀毒软件。 as an adjective = useless; incapable, e.g. 那个杀毒软件真没用。or 都怪我没用，让你受委屈了。 Q2. Is 没用 always the same as 没有用？ ——Yes, as a word, I can't think out an exception.