One basic rule: Never use would or could in subjunctive clauses starting with if. Sentences nr 2 are the only correct ones, according to established E grammar rules.
One exception would be:
If+should/would can be used when expressing desire, request, wishful thinking, or 'in case':
1.I would change my ways, If I should love again...
2.If I should die (=if this happens), I want you to remember me that way...
3. I would be happy if I would get the chance to meet you again. (= I wish I could meet you again).
Also, you can re-write your sentences by omitting 'if':
If I had met him, I would have given you. / Had I met him, I would have...
If I had seen it, I would have told you. / Had I seen it, I would have...
- For Teachers