1. Which is the safest or easiest country to get married without any issues?
Both the countries will be having their own laws which may be stringent to each other. The laws of the countries are to be followed in this regard accordingly.
2. How long will it take to get all the legal marriage documents?
It depends on which place you apply for registration of your marriage. In India the marriage process is long and time consuming.
3. Which type of marriage is easy and best for us? (None of us wants to change our religion)
In India, you may have to follow the procedures of special marriage act.
4. Will she also have share in my property/earnings/assets after we get married?
5. Once she get married, will she have Indian nationality?
It is not automatic, she has to undergo the proper formalities in that respect.
6. Is it possible to get married in neutral country and get citizenship of that country, if yes, which is easiest country?
What is neutral country?
You can get married in either of the country following the prescribed rules of the country chosen.