Possessive Nouns are often used as adjectives true or false

No, possessive nouns cannot be used as adjectives.

Explanation:

Possessive noun shows the ownership and possessive adjective defines and modifies the noun to show the ownership. Possessive adjectives are not formed by adding apostrophe + s to possessive noun.

Possessive adjectives are my, your, his, her, its, our, their. The possessive pronouns that replace the noun are: mine, yours, hers, his, its.

For example: his head is big. (His is possessive adjective)

That money is ours. (Ours is possessive pronoun)