Some people say a dog=one, dogs=ones, the dog=the one=that, and the dogs=the ones=those. It's a rule of thumb, but what I found was that this is not always correct.
What is the proper way to use "ones" or "one's" this word in sentence?
However, "one and only one" adds emphasis to the fact that there is only one, and draws attention to it. For example, the student who is the only one who failed, might feel more ashamed if the teacher uses "one and only one", as the teacher might be perceived as purposely drawing attention to that fact, for whatever reason.
"One's" is a contraction of "one is" or "one has." It is also the possessive of "one." Examples of these are: One's mood can be affected by the seasons. (possessive) One's the smallest positive integer. (contraction) "Ones" is merely the plural of "one." This is the usage you are looking for here. In English, "one" can sometimes be used to indicate individual units of something. Here are some ...