For this series am putting it as Trivia as I can't find the changes between the novel and anime, there also a manga counterpart to Index so for this series there is going to be multiple thread. This thread will not only contain Trivia but also the changes between three different version for Index and two different versions of Railgun as well as Accelerator.
Update: Do note the changes will be written under Note which will be at the end of every arc, also Railgun has some episodes that are original hence I will state if the episode is original or not. Added the whole of Index Season 1 plus 1 episode from Season 2 as that episode is link with that arc which I had stated clearly. Railgun Season 1 to be added tomorrow along with Index Season 2 if there is no delay that is.
Update 2: Added Railgun Season 1 and Index Season 2 as promised, I will added Railgun Season 2 and Index Season 3 three to four weeks from now which could be second week or third week of April. On the side note Accelerator Season 1 will air on July, hence the Trivia should be up once the series ends as it would be easier for to comply the information and post it in one shot instead of update it on weekly base or monthly base.
Update 3: Added Railgun Season 2, I will add in Index Season 3 at the end of April so look forward to it as I would give the site that I got this information sometime to get the information that I need to put it up here.
Episode 48 - Eternal Party (Original Episode)
Major Event
STUDY's nefarious plot has been stopped and Janie and Febri are free of their bondage.
The Academy City Research Exhibition Assembly of the year begins.
Shinobu, Febri, and Janie leave Academy City.
Trivia
This is the first actual time Aomi is shown to be on duty as Judgment.
The full capabilities of Kongou's Aero Hand is shown for the first time.
The mechas that uses Mugino's Meltdowner may be a reference to the FIVE_Over series.
Aritomi is shown to be try and attempt suicide via a gun to the head. However, in the original manga, Kiyama Harumi was shown to do the exact same thing once her plans became unraveled and when the AIM Burst started its rampage. It is unknown why Harumi's attempted to suicide was taken out.
Misaka 19090 is revealed to be the clone that was in the Testament machine as she tried to inject emotions into the Misaka Network.
only my railgun is the only opening not used as an insert song this episode.
Shinobu is shown wearing a gothic lolita outfit for the first time in the present day.
The denouement scene shows that Mikoto has changed her hairpin (from the previously plain one to a floral one), implying that Janie, Febri and Shinobu's departure occurred after August.
Accelerator and Last Order are shown with both of them conscious. These further supports that the end of the episode occurs way after August.
Touma is shown to be doodling a drawing of Index on his notebook.
After the departure of Febri, Janie, and Shinobu they mention that the Liberal Arts City trip is the next day, which suggests that their departure occurred during September 2, a day before the Mikoto and company arrive at Liberal Arts City.
The scene where Saten is shown studying "something" related to Kongou Airlines is used as a flashback this episode.
Scenes from episode 05, 14, and 15 are reused as a flashback regarding Accelerator.
The explosion of the missile in the upper atmosphere/space is the exact animation used for sun-rising sequence in the second opening.