Why those not open even though i have killed 250 with varible zoom and 500 with chrome lined???
I'm having the same issue. ffs This game is so sophisticated. Just make the challenges all available from the start..
In order to unlock anything in this game you have to go under the operations menu, and look for the Var. Zoom Master, and unlock it in order to get the Cobra Suit. If you're going after the other one you need to find the Chrome attachment in operations and have that selected. This goes for all attachment's.