It is impossible to construct a sentence in which "your" and "you're" can be used interchangeably while keeping the sentence grammatically correct. This is because "your" is a possessive pronoun, and "you're" is a contraction for the phrase "you are."
Possessive pronouns are separated into two categories: strong possessive pronouns (i.e. his, hers, yours, mine) and weak possessive pronouns (i.e. my, his, its, your). Strong possessive pronouns refer back to a noun or noun phrase. For example:
The tan-and-white corgi is hers.
In this case, the noun/noun phrase (the subject) that the strong possessive pronoun refers back to is an implied "she."
Weak possessive pronouns, on the other hand, function as a determiner (i.e. the, a, an) for a noun/noun phrase. Using the same example, we can rephrase the sentence:
Her corgi is tan and white.
The pronoun "her" describes the corgi. It clarifies to whom the corgi belongs. Due to their descriptive nature, weak possessive pronouns are sometimes known as possessive adjectives. Yours is a possessive adjective. Combining it with the noun it is describing creates a noun phrase.
"You're," meanwhile, is a contraction for the simple sentence "you are" (of course, you can't end a sentence with a linking verb, but for the simplicity's sake, we'll categorize it as a simple sentence). There is a subject, "you," and a verb, "are." "Are" is a linking verb, so the predicate adjective/noun that follows completes the sentence.
It's impossible to use "your" and "you're" interchangeably because one functions as a determiner and creates a noun phrase; the other forms part of a sentence and combines with a descriptor to create a complete sentence.