Can't use Command_Block

If I am a host, open the LAN and close the cheat, I will not be able to use the command_block(I cheated on myself)
If I am a host, open the LAN and close the cheat,I think I can use the command_block.
I can't open the command_block GUI
1.open the LAN
2.close external cheating
3.you can't use the command_block.