Possessive plural nouns

SOURCE: what is a plural noun

Consider a noun such as BOY. When there is only one (a single one) you can say something about the boy, or about a boy.
So you use the form BOY when there is a single one. This form is called the singular form of the noun BOY.
However if you are speaking about or pointing at a group ( of people ) in which everyone is a boy you use the modified form BOYS. This form is called the plural form of the noun BOY. The word plural means many.
The plural of a noun is usually made by adding s to the singular. It is pronounced S after a p, k, or f sound. Otherwise it is pronounced Z.
There are certain exceptions to this rule, the ones that come to my mind are: one child, three children; the man, 10 men; one woman, many women; a single knife, 12 knives; a potato, several potatoes; the top shelf, all the shelves.
Note: When you look for the meaning of a noun in a dictionary, you look for the singular form, although the plural is indicated in full if it is irregular (does not follow the rule).

SOURCE: what is a possessive noun

Abstract nouns.
There is no such thing as a possessive noun. It should be possessive pronoun.

SOURCE: what is a plural noun

Consider a noun such as BOY. When there is only one (a single one) you can say something about the boy, or about a boy.
So you use the form BOY when there is a single one. This form is called the singular form of the noun BOY.
However if you are speaking about or pointing at a group ( of people ) in which everyone is a boy you use the modified form BOYS. This form is called the plural form of the noun BOY. The word plural means many.
The plural of a noun is usually made by adding s to the singular. It is pronounced S after a p, k, or f sound. Otherwise it is pronounced Z.
There are certain exceptions to this rule, the ones that come to my mind are: one child, three children; the man, 10 men; one woman, many women; a single knife, 12 knives; a potato, several potatoes; the top shelf, all the shelves.
Note: When you look for the meaning of a noun in a dictionary, you look for the singular form, although the plural is indicated in full if it is irregular (does not follow the rule).

SOURCE: what is a possessive noun

To express possession (ownership) in English one appends an apostrophe (') followed by s
The nose of the moose can be expressed as the moose's nose.
The rule is straightforward. When the noun to which the ownership refers to is the plural, the rule can be applied as stated above append ('s). However if the mark of the plural is s (regular plural) some people want to use the rule above, some others say that the last s should not be written.
Eaample: The hind legs of the wolves can be expressed as the wolves's hind legs or the wolves' hind legs. In the first expression you have wolves's while in the second you have wolves'.
Both rules are correct, but nowadays the tendency is to use the second form. It is a matter of usage.
If you are a student follow what your teacher says. When you write your own books, choose the one you want, but if your editor insists on using the other one, you have a problem.