For the 1st problem, you will need to change the permissions and ownership of the plugin directory and all the files underneath.http://linuxcommand.org/learning_the_shell.php
You may be able to do it from WinSCP, just right click and go to properties. Be sure to check the box to set permissions recursively.
Your template problem is almost likely the same issue. In this installation step, you copied some files over.Via scp or other tool, copy the files “resource/snmp_queries/*.xml” into directory ”<path_cacti>/resource/snmp_queries
You need to go to those files and check that their permissions are correct.