Tenses for two clauses joined by "if only"

1. Our school had won the match if only we have concentrated.
2. Our school would have won the match if only we would have concentrated.
3. Our school would win the match if only we had concentrated.
4. Our school had won the match if only we would have concentrated.
5. Our school would have won the match if only we had concentrated.

Tell me which one is correct.

Solution 1:

Only sentence 5. is correct. Whenever if only is used in a dependent clause, the independent clause must take the conditional perfect (or present, etc.) tense.

Solution 2:

5 is the only correct one, but you have the additional near-miss on 3:

Our school would win the match if only we concentrated.

A hypoethetical future result based on a possible current action, as opposed to the past/past combination you have in your statements.

Solution 3:

The fifth one is the only one which doesn't sound marked to me, as a native English speaker. I believe that some speakers of American would consider the second one acceptable too.