You can't use "one" as a pronoun to stand in for "a person" or "someone" in quite this manner; you'd have to rewrite sentences ii and iii as:
If one wants to succeed, one should work...
This pronoun is occasionally useful, but suffers one major drawback: It sounds too old-fashioned and pompous for most purposes. That's a pity, because in this politically correct world, using "he" in such sentences is seen as sexist, and should therefore be avoided.
Various techniques have been tried, not all of them very elegant. One such is to write "he/she" or "(s)he", but it looks ugly and how are you supposed to pronounce it? You could write "he or she" or "she or he", but that quickly becomes tiresome. Some writers alternate between "he" and "she", but I find that quite irritating.
An alternative is to simply use the plural -- it's not always possible, but it usually is, and it is then the simplest and most elegant solution: "If people want to succeed, they should work..."
It's also possible to use "they" with a singular antecedent: "If a person wants to succeed, they should work..." This technique is actually hundreds of years old, but fell into disuse a few generations ago and is thus seen by some readers as "new-fangled" or simply "grammatically incorrect"; it certainly looks strange if you've never seen it before.
In this case, though, you can avoid the issue altogether by recasting the sentence like this:
A person wanting to succeed should work...
Anyone wanting to succeed should work...
Now, "wanting to succeed" is an adjective (actually, it's an "adjectival phrase"), and we only have one clause -- so no need for a pronoun.
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