1. How to change gamemodes in Minecraft
For example: switching into creative mode can allow players to get themselves out of a jam they wouldn't be able to get out of in survival. Or even build a house without having to scavenge for materials.
There are currently four different gamemodes, one of which is exclusive only to Minecraft Java Edition. "Survival," "Creative," "Adventure" and exclusively, "Spectator."
How to change gamemodes while mid-game
Firstly, players must have created their own single-player world. Regardless of what gamemode was chosen at the beginning, players will be able to alter their gamemode in-game.
Once they're in the overworld, click the escape key and bring up the Minecraft menu. There should be a button that says "Open To LAN."
Hit that button and players should see a menu titled "Settings For Other Players."
Don't mind the gamemode button, but click the "Allow Cheats" button so that it says "On."
Once that's done, hit "Start LAN World."
Opening a LAN world means, technically, opening a single-player world up to multiplayer activity. However, with LAN multiplayer, it's required for players on the same single player server to be on the same internet connection, and close to one another. So, rest assured, there will be absolutely no unwelcome strangers joining your single-player world.
If completed successfully, there should be a text box in the left hand corner of the screen that says, "Local game hosted on port XXXX."
Note that this will reset every time players exit their worlds. So next time players log into their world, they'll have to redo this process to open the LAN world again.
Once this has been done, players will have complete access to any in-game cheat, including the ability to change gamemodes.
The command to change gamemodes is "/gamemode"
To switch to Survival Mode, type out any one of the following commands: "/gamemode survival" "/gamemode 0" or, "/gamemode s"
To switch to Creative Mode, type out any of the following commands: "/gamemode creative" "/gamemode 1" or, "/gamemode c"
To switch to Adventure Mode, type out any of the following commands: "/gamemode adventure" "/gamemode 2" or, "/gamemode a"
To switch to Spectator Mode, type out the following command: "/gamemode spectator"
Be warned that if players have chosen "Hardcore" as their initially selected gamemode, they will not be able to return to regular survival upon switching to that gamemode. They will, however, still have access to creative, adventure, and spectator modes.
Adventure Mode is often used for parkour and adventure maps, since its primary feature is taking away the player's ability to break and place blocks. Which is perfect for the mechanics of adventure maps, which generally run in a progression that can be easily messed up if players can break and place blocks. But, it's not very useful in a regular Minecraft world.
Spectator Mode does exactly what the name entails. It's the gamemode players get put in when they choose to keep a hardcore world after dying. Their entire in-game character is stripped away, and they're left just roaming the world unable to interact with it.
How to change gamemodes from the Minecraft World Creator Menu
Don't want to switch gamemodes mid-game? No problem. There are methods to allow cheats, including the ability to change gamemodes, through the initial world creator menu.
First, click "Create New World."
After finishing the final touches on a world name, hit "More World Options."
From there, players can do a variety of things, such as edit the predetermined randomly generated world, and enable cheats. Click "Allow Cheats" once again so it says "On."
Players are now free to switch gamemodes mid-game and don't have to keep redoing the process each time they quit the game or exit their Minecraft world.