4. Type in "/gamemode" (without the quotes) followed by a space, and the mode you want to switch to (Creative, Survival, Adventure, or Spectator), then hit the Enter key. So, for example, if you want ...

Changing gamemodes in Minecraft might be considered cheating in some cases, but it can allow players to do a variety of things mid-game.

The only way to switch an existing world to Hardcore mode is to use a third-party app to edit the game's files. How to change game modes in 'Minecraft: Java Edition' 1.