.bin can be anything arm9.bin is the main binary the DS runs (and could house the title screen), arm7.bin in commercial games is a helper binary to handle some aspects of the hardware (you can swap them between games of similar vintage or just before and after most of the time they have so little unique to them), and things in the overlay folder are like the arm9 but swapped in and out of memory (they too could possibly contain the title screen, some games even stuff everything into ridiculous numbers of overlays). Ignoring the header and whatnot stuff in the main directory along with the arm9.bin then the other main .bin of note usually gets called utility.bin and is one of the ways download play works, speaking of which
.srl is quite often the download play (it is basically another DS ROM, opened with all the same programs) but I have seen it function as another aspect of the ROM before.
.vx I already mentioned is video files.
.sdat if there is one (would be surprised if not) is the sound for the game.
As for corruption then varies with what you need. Some people will copy and paste other parts of the ROM, some people will use a hex editor, some people might need to corrupt the file but only within certain ranges (you might well have had cheats in the past say don't put this value over 99 or it will crash, same idea here). There are tools though that will replace the contents of a file, or section thereof, with random junk though.
http://www.romhacking.net/?page=uti...&perpage=20&title=&desc=corrupt&utilsearch=Go should have a few if your hex editor selection or own programming options don't do it for you.
Before jumping to corruption though I would do both ROM shrinking (maybe also run everything through decompression tools -
https://gbatemp.net/download/cues-gba-ds-compressors.33556/ ) and opening in a tile editor to press page down a lot, repeating with it set with the common GBA 4bpp, 8bpp and custom widths for both of those. Also finding it in VRAM (desmume and no$gba should be able to tell you where it is in VRAM with their VRAM viewers) and searching for the same data or chunks thereof in the ROM/decompressed files.