This is the most reliable, permanent solution. It works on every version of IGI 1 (original CD, RIP, or GoG version). We will bypass the in-game cheat system entirely and directly modify the level completion flags.
Sometimes the players folder gets corrupted. igi 1 all mission unlock key fixed
Create a new text file called unlock_all.reg (or download it from a trusted abandonware archive). Paste the following code exactly: This is the most reliable, permanent solution