how to know the version of the game that we are playing?
Depends on the game. Some give it on the main menu or in a config screen. Some report it in the properties of the main game .exe file. With some games you can find it in a version .txt file in the game folder. Others don't report it anywhere and you have to take note of the release date or the game/update to match it with the right trainer.
What's the game? Perhaps someone here knows exactly where to find it for a given game