I've made TL-DR (too long didn't read) for every paragraph so if you are in a rush(or just don't feel like reading from a newb), you don't have to endure all my foolery.
Hi tempers, I recently was foolish enought to let my 3DS in sleep mode with the WiFi on, so naturally she downloaded the damn update via spotpass, I'm waiting for Smealum to release his exploit since I'm on 7.2 and I missed gateway because I updated from 4.5 and then I found out gateway would only work on 4.5 or less.
So my fear was that I accedentally and mindlessly pressed A throughout the process of updating the console in some kind of rush to play a game, maybe when I'm sleepy or something (it happened once to me) thus I started searching for a way to get rid of the damn update, and I think I found one way, I'm still testing it so I'm not 100% sure this will work for everyone.
TL-DR Im a fool, I let my 3DS to download an update and I'm scared.
So I started searching for a way to delete it, as I mentioned above, and something with the EXTDATA folder, so I went on and backed up my SD card and started the process.
First thing I did was to eject the SD card from the 3DS and boot it up, and it didn't ask me to update. I put on the SD and booted up, she ask me to update her. This was ovious, the update data was on the SD card, or at least some data that told my 3DS that there's an update.
Next thing I did was to search for the folder EXTDATA, and found that this folder actually has the extra data of all my eShop titles, I have like 60 something so there were lots of folders. I also found this in 3DBrew:
00000082 0000008f 00000098 Home Menu extdata, this contains home-menu savedata and cached icons for applications.
00000200 00000210 00000220 System Settings extdata added with 2.0.0-2.
So I figured that if I deleted the content of these two folders, something would happen (again, my SD was backed up whole so this wasn't a risk) and proceeded to do it. First the 3DS shpwed me a message that it is buidling the filesystem of the 3DS (or something like that), to my surprise when she finished all of my eShop games icons showed like presents, like when you first download them, and no update at all. I don't know if the update itself was saved in the SD, maybe one of those folders contained a file that tells the 3DS that there is an update downloaded and that it needs to be intalled.
Also it is important to note that although the games showed like presents, they worked normally, and no savefile was lost.
TL-DR I´ve erased the folders 0000008f and 00000210 from the EXTDATA folder in my SD card (its ubication varies between consoles so just search for it in the Nintendo 3DS folder in the root) and the update message dissapeared, all my games were wrapped like presents and were functional as before. I didn't noticed anything apart from the 3DS creating the extra data again.
I'm now doing an experiment, I will let MY 3DS in sleepmode connected to the internet and wait for it to download the update, but this time it has an empty SD, I've put the SD in the 3DS and when I read it in my PC the only folder it has is the 0000008f and its files, it has to be because it builded the extra data for the menu, so if the update prompt appears again, and a new folder appears in the SD, that folder has to be where the update files are, if it doesn't apppear a new folder, and I erase the 0000008f folder and again the update prompt dissapears, forever, this means 1) that the files are actually saved here, or 2) in this folder lies a file that tells the 3DS that there is a update downloaded.TL-DR I'm making a new experiment, with a new SD card reciently formatted and let the 3DS downlaod the update, to see if it makes a new folder and have some conclusions.
Well if you made it this far, thanks! and hope this is helpful to someone, and sorry if this was already posted, but I coudln't find it, so decided to make this post to help those people with the same predicament as me. Any feedback will be helpful.
Sorry if my English is bad or inconsistent, it is not my native language.