unlock impossible sets

hi guys
i used to play gears of war 3 system link on my jtag i never use xbox live i have edited my profile using player storage editor but i want to know how to unlock impossible sets of characters and skins watched many videos of unique characters and skins but i don't know how to these stuff so plz help
thanks

 

change to what ever character or gun skin on jtag. save and quit an then play on retail.