What tense should the subjunctive mood guided by if be used?

The sentence pattern is "if+ subject+verb past tense (be verb uses were), subject +would/could/should+ verb prototype". If the weather is fine, we will go to Shanghai. If the weather is fine, we will go to Shanghai. (Actually, the weather is bad)

Indicates a situation contrary to past facts. Its sentence pattern is "if+ subject+past perfect verb, subject +would/should/may+have+ verb past participle". If I had taken his advice, I wouldn't have made such a mistake. If I had followed his advice, I wouldn't have made such a mistake. ?

The sentence pattern is "if+ subject+verb past tense /should+ verb prototype /were to+ verb prototype, subject+would/may/should+verb prototype". If you drop the cup, it will break. The cup will break if it falls. (Actually, I didn't fall)?

Subjunctive mood is used to express a hypothesis, not an objective fact. It is a condition, not necessarily a fact, or contrary to the fact. Subjunctive mood is expressed by the special form of predicate verbs. Moods in English can be divided into declarative mood, imperative mood mood and subjunctive mood. Subjunctive mood refers to the assumption that the speaker makes is not true, or it is difficult to realize, or even expresses the opposite concept. In addition, subjunctive mood is also used when expressing subjective wishes or expressing some strong feelings.

Subjunctive mood is used to express imaginary false, contrary to the facts or difficult to realize, and also used to express subjective wishes or some strong feelings. That is, when a person wants to emphasize that what he says is based on his own subjective thoughts, wishes, assumptions, guesses, doubts or suggestions, rather than on objective reality, he uses subjunctive mood. Mainly an expression of English grammar.

Conditional sentences can be divided into two categories, one is true conditional sentences and the other is untrue conditional sentences. Unreal conditional sentences indicate that it is impossible or even impossible to assume or actually happen, so subjunctive mood is adopted.