Hi
i have been to Andamans for the last 4 years consecutively, i love the place
1. Long Island - very quiet no cars only motorbikes and cycles / Hutbay (Little Andamans) nice beaches as well but connectivity only from Port Blair for both locations
2. there is bleaching due to the water temperature increase 2 years ago
3. there are a few but i suggest Andaman Bubbles because i have dived with them for the last 2 years, i did my open water with Dive India 3 years ago and dived with Barefoot also but i still suggest Andaman Bubbles
4. Wild Orchid / Seashells / Symphony Palms / Munjoh / Silver Sands
5. Havelock is more happening than Neil, so if you want peace and quiet then more on Neil and less on Havelock and vice versa
hope this helps