Question

1. If you do it, you will be successful.

2. If you will do it, you will be successful.
(Is #2 grammatical?)

3. If you will[wíl] do it, you will be successful.
(What about this one? In the if clause, 'will' is stressed, which indicates the volition of the subject. In this case, can we use 'will' this way?)

4. If you will[wíl] do it, you have to make a lot of money.
(Is it grammatical,too?)

Answer 1

2 is not ungrammatical; it's simply not used. "If" introduces a possibility, not a fact; thus, the future tense is not needed.

I've never heard or read any "If" clauses like these with future tenses correctly used.