Crysis 2 keys were region-locked (e.g., Russian keys were cheaper but wouldn't activate in the USA).
You found an old DVD copy and need the serial code from the manual. crysis 2 product activation key
Crysis 2 Maximum Edition is regularly sold for $4.99 on official sales. Is it worth saving $2 to risk account termination? No. Crysis 2 keys were region-locked (e