6 month double entry India tourist visa (in Iran), 2 pass.

I am soon applying for an Indian tourist visa (in Iran), and then immediately flying to India (arrival: Chennai).

I have 2 passports, Iranian, or Canadian (Iranian birth, Canadian residency), traveling in Iran (on the Iranian passport), will soon be applying for an Indian tourist visa, i have some interest to know more about which passport I should use?

Does it many any difference? Is up to me?

Are there any usual difficulties?

I am interested in a double entry, 6 month tourist visa. I've emailed the consulate, and embassy in Tehran, and Bandar Abbas, but they don't seem to answer emails, before I visit these offices in person, just wanted to check with other dual nationals with similar experience, or a kind of expert at Indian tourist visas.

I also wanted to ask about how to make my application more professional/complete? Is it wiser to book the entry, and exit flight before applying for the visa? Also, i am thinking to make an intenerey showing how I plan to travel in India for 4 months (and the 2 months in Nepal), thats why I need a 6 month double entry.

I will enter one way Iran-Chennai, and exit one-way in the other direction, Dehli-Asia.

Thanks for reading