Some questions (anime to vol 14 and 15)

Hi all,



I watched the animes and really enjoyed them, I watched index season 1, then railgun 1, then index season 2 and finally railgun s. I decided to pick up the novels from book 14 and have read that and vol 15.



It seems to flow from the anime quite well but I have a bunch of questions (naturally some spoilers below):



1. Are there any events or bits of info in the novels that isn't in the anime that I should be aware of?



2. Are there any volumes that are considered "must reads" if you're transitioning from anime to novels?



3. In vol 15 Uiharu meets Last Order who is constantly referring to herself as Misaka but doesn't seem to react to the fact that a kid who looks a lot like Mikoto is calling herself Misaka. Is Uiharu at all aware of the clones? Or is she just doing a Touma?



It seems odd that she wouldn't at least find this slightly off.



4. At the end of volume 14, it doesn't explain how Touma got back? This is it just assumed he did or do they pick up a book or two later? If the latter do they do stuff like that often?



5. What is the purpose of these organisations such as GROUP, this is something I didn't quite get at the end of Season 2 and I'm still a bit confused as to why they exist.

Some questions (anime to vol 14 and 15)