Which following statements are true

Systemd start mysql is a command to start a mysql service.

A command rm $-$rf $/$ will forcefully remove in a recursive manner all files and directories located in the root path.

If a file is created with default permissions $666($without the permission to execute$)$ and the umask is set to $002$ the owner$$s group users will have the permission to write such a file.

Adding to a command $>>$ error.log will redirect its output channel STDERR with the append option to the error.log file.