Can I use PHP shell_exec() on my PocketMine plugin? And if it's possible, can I submit a plugin which uses shell_exec()?
I would nto trust any plugin that runs any application for me there is no real need for it. what exactly are you going to run
The only example of a plugin which executes system commands which was accepted is: http://forums.pocketmine.net/plugins/pitemp.405/
To add to my post: The rules stated that if your plugin is designed to be platform-specific, it's OK. But don't upload your plugin with some DLL files, because the plugin is not supposed to be platform-specific but DLL can only be used by Windows.
And there can be platform specific features, just so long as the plugin functions or fails gracefully on all PocketMine platforms (Android is often an exception as PocketMine doesn't really support android all too well).