Answer:
2. Joel himself ate all the spaghetti before anyone else could have some.
Step-by-step explanation:
Intensive pronouns have the same form as reflexive ones (myself, yourself, herself, ourselves etc.) but their meaning is different.
Intensive pronouns only emphasize their antecedent and, truth be told, are not important for the meaning of the sentence; the sentence is perfectly grammatically correct and understandable even if they're left out.
However, the question here is their proper use.
Sentence 1) uses the incorrect form "theirselves" which doesn't exist. Correct form would be "themselves".
Sentence 3) lacks antecedent. "I myself" would be proper intensive pronoun use.
Sentence 4) needs object pronoun "her" because Luisa asked other person for autograph, not herself.
Finally, sentence 2) uses intensive pronoun "himself" correctly. It emphasizes that Joel alone ate all the food and the sentence would be just as reasonable if we left out the pronoun.