4 and 6 are not correct, 2 and 5 are very similar (almost the same), and the others are all different meanings.

You don't have to work. (The words HAVE TO are not as specific as NEED TO) There is no need to work. ( The words "need to" are used when there is a requirement or urgency. For example, I NEED to work to make money. The sentence is a general thought that might involve many people) You don't need to work. (This has the same meaning as the above sentence but stresses that YOU don't need to work while others do need to work.) It's not needed to work. (This is not a correct expression) It's not necessary to work. ( This is another general thought. It can apply to a number of people. It is in contrast to saying, "It's not necessary for YOU to work" or "It is not necessary for HIM to work".) There are no needs to work. (This is not a correct expression. You could say, "There is no NEED to work) Hope this helps

It's not needed to work... has a different meaning. It is something ( a key,). It's not needed to work = the Key is not needed for the car to work. There is no need to work. Work is an uncountable action. We do use works as a countable noun, as in "His many paintings are blue".."His many works of art are blue"

1-You don't have to work. 2-There is no need to work. 3-You don't need to work. 4-It's not needed to work. 5-It's not necessary to work. 6-There are no needs to work. numbers 1, 2, 3 and 5 are correct, although 5 sounds a little unnatural There is a slight difference of meaning between 1 and 2. 1 means that there is no obligation to work- you can decide for yourself whether or not to work. 2 means that it is not necessary. 2,3 and 5 all mean the same I hope that's helpful