A few queries and help for planning

Hey,
I am planning a shoestring budget trip to the Andamans for 2 people (both Indian males) from 18th Dec to 28th Dec. Just a few things I wanted to get cleared regarding it:
1) How long does the ferry take to reach from Chennai to Port Blair.
2) Current cost of the ferry.
3) If we can sleep directly on beaches in case we have sleeping bags
4) If we can expect to get budget accommodation (Less than Rs. 200/night for 2 people.) Where are the offbeat beaches where we might get these (Havelock will be packed at this time of the year I assume. Any other options?)
5) (Maybe stupid question but) There are ATM's on the islands I hope.
6) Do we need permits for any place? (Considering we are Indians)
7) Can we book a ferry in advance or should we do it after reaching Chennai? In that case will we get a ticket easily?
8)Must see places and things to do. (Regardless of the cost.)

I can answer a few....

1) Around 66 hrs....
2) Look here http://www.andamanworldtravels.com/stepin.php
5) Yes in port blair theres plenty & havelock too....
6) for great nicobar yes..... but not anywhere else
7) For Ship Tickets Booking, one has to personally go to any of the aforementioned office with 2 copies of passport size photographs, fill up an application form & then do the booking.
8)Whole part of Havwlock & Neil, Long Island...., Ross & Smith

Thanks!
Also, are their any private ferry (not cruise) operators to Andaman from Chennai? And is there any change in frequency from 4 sailings per month?

Sry no idea abt that