If you insist on a "key," buy one legally. Sites like Green Man Gaming, Fanatical, or Humble Bundle sell official Steam keys. You get a code instantly via email. You type it into Steam (not a sketchy launcher). The game unlocks forever.
If you have already downloaded a file named resident evil revelations 2 license key.txt and clicked on it, follow these steps immediately: resident evil revelations 2 license key.txt
To understand why a .txt file won't work, you need to understand the game's architecture. If you insist on a "key," buy one legally
Resident Evil Revelations 2 uses Steam CEG (Custom Executable Generation) and Denuvo (in older patches). This means the license is tied to your Steam account, not a local text file. If you insist on a "key