1. What is the appropriate form of the conditional mood to be used after I wish/if only ? I wish I were stronger

The appropriate form of the conditional mood to be used after "I wish/if only" is the past simple or past perfect subjunctive form. Let me explain each sentence and its corresponding conditional mood form:

1. "I wish I were stronger so that I could participate in the competition."
- Here, we use the past simple subjunctive form "were" after "I wish" to express a hypothetical or unreal situation in the present. The use of "could" further emphasizes the unreal nature of the situation.

2. "The Smiths live in the village, but they wish they lived in the city."
- Again, the past simple subjunctive form "lived" is used after "they wish" to express their desire to live in the city, which is different from their current reality.

3. "I wish he could have visited my grandmother yesterday, but he had a job interview."
- In this case, we use the past perfect subjunctive form "could have visited" to express a hypothetical past situation that did not happen. The use of "but he had a job interview" adds the justification for not being able to visit.

4. "Kate wished she wouldn"t have to watch this frightening movie again."
- Here, we use the past perfect subjunctive form "wouldn"t have to watch" to express a regret or desire for a different past situation. The use of "again" suggests that she has already watched the movie.

5. "Matthew didn"t go to university after school. Currently, he wishes he had gone there."
- In this sentence, we use the past perfect subjunctive form "had gone" to express the regret of not going to university after school. It indicates a desire for a different past outcome.

6. "I wish you would read more scientific books in the future."
- After "I wish", we use the present simple form "would read" to express a desire for someone to do something in the future. The use of "more scientific books" specifies the type of books.

7. "If only Ted had the chance to travel when he was a teenager."
- Here, we use the past perfect subjunctive form "had" to express a hypothetical or unreal situation in the past. The use of "If only" emphasizes the desire that Ted had the chance to travel as a teenager.

By using the appropriate conditional mood forms, we can convey different desires, regrets, and hypothetical situations associated with "I wish/if only" statements. Keep in mind that these forms might vary depending on the context and tense used in the sentence.