Killer Instinct 2 isn't a NeoGeo game so the Neo bios is irrelevant. You need the game rom and CHD. If you have both and mame reports you have files missing then your source is hosting out of date roms and you need to source them from somewhere that has up to date one's.
If you check the MAWS website against the files mame is reporting mising you should be able to see if its the rom, CHD or both that are missing files.
Make sure your Killer Instinct 2 rom is the parent rom (Killer Instinct 2 v1.4 - kinst2.zip), also make sure your CHD folder (kinst2) is in the mame/roms folder and that the CHD inside it isn't zipped.