1. there's several ways,one is to swap the NIS(non interactive sequences) in the story mode when facing the bosses be it pre or post fight and you will see the fatality done to them. two,which is exclusive to shao kahn is to swap the (insertcharnamehere)_ladder file with a fatality,then you will see the fat. done to kahn.
however if you want a traditional and definitive way here's what you do,get the C59 codelist i posted as an article in psx scene(it's the latest mk9 article) install it on ps3usercheat,and then activate the Set (insertnamehere) as Char 2 in C59. codes and then go to the challenge tower,go to challenge 59,activate the code while on the loading screen,then beat sheeva,but DONT finish her,then beat her again 1st,then beat the character of your choosing and finish him/her off. (keep in mind,the finishable bosses npcs pack 5 i posted earlier simplifies a part of the process by preselecting what character you want to play as and as well in which background/arena you are going to fight in) if it's a bit unclear,you can ask TimeRevolver031,i think he can explain it better to you(sorry,i'm a bit nervous right now XD)
2. if you are referring to the bosses pkgs that contain the UI files(aka images) WILL NEVER WORK on komplete edition,since it's basically 1.05 mk9,and previously,on 1.00 and 1.01 mk9 you could install the UI files to the HDD,by what seems to be either a glitch or a dev code we haven't yet found,but either way,on 1.02 and onwards,they "fixed" this,and now it's impossible,you have to replace the files in the backup(PS3TOC method) yes or yes.
Double Barrel Shotgun>AK47.