Are these sentences right?

[jennie77]

1. People can understand how slightly variations of DNA develop effects on human health.

2. If I could go back in time, I think that I would have told her that for she could have helped me.
The actual tense of "If-clause" is present, but the other clause has past tense here. Is it alright?
Or can we say that " If I could go back in time, I think that I would tell her that for she could have helped me."?
Quite tricky.

Thanks in advance.

[Mister Micawber]

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1. People can understand how slight variations of DNA develop effects on human health.

2. Present Conditional (II): If I could go back in time, I think that I would tell her that she could help me.

Past Conditional (III): If I could have gone back in time, I think that I would have told her...
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