Error "help: permission denied" when using ADB
First of all help is no actual command that comes with the Linux system (even though many systems like Ubuntu have one). If you would like to see valid commands, just list all files inside /system/(x)bin with the appropriate ls &lt;directory&gt; command.

If help is listed there then it may not be your usual help command you know from windows.

It may also be a limitation by the manufacturer so that terminal access is restricted to the system only.