Hi Mrityunjay, you have asked a very important question. This however does not have a very straightforward answer.
1. You should always review any document given to you by builder. This is because the document/agreement may have clauses which take care only of the builders interests and not of the buyer (you). Hence , having a competent third party to review it, is always safe. The best people to perform such a review are lawyers. Always select a good property lawyer in Pune for this.
2. Now , even after a lawyer has recommended changes to the draft, there is a big question mark on whether or not the builder will agree to make these changes. Most average and small builders will make the changes after trying to understand why you want them. But a big builder like Kolte Patil, Kumar, Paranjape etc. will simply not entertain such changes.