Yes and no. Mods like Ziggy’s Mod or FC3 Reloaded permanently change game files, which can lead to corrupted saves or multiplayer bans (if you forget to disable them). The is temporary. It runs in RAM only. Close the trainer, restart the game, and Far Cry 3 returns to 100% vanilla.
If you want to avoid third-party software, you can enable limited developer "cheats" by modifying the game's launch parameters: Right-click in Steam or your launcher. Properties Launch Options -GameProfile_GodMode 1 -GameProfile_UnlimitedAmmo 1 Steam Community far cry 3 trainer 0101 exclusive
And for the first time since he’d pressed F4, he missed the fear. He missed the reload. He missed the moment when a single bullet mattered. Yes and no