can not change minecraft mode and player access
Solution 1:
You can open the server to your Local Area Network.
If you pause the game with esc, you will find a button: "Open to LAN". This will make your world available to play for other players, but only if they are using the same local network, eg. they are connected to the same WiFi network or to the same Ethernet network. Like this, you don't need to worry about other players that you don't know about getting into your world.
When you are about to start the LAN world, select Cheats: ON. Now you can run commands in a non-cheat world.