[deanhills]

nice one frm you,
can i ask you: some plugins won't work with me suck as Multi user badge(forum rank img), i used manythings
i didn't use the latest version 1.8.7.. should i update forum to make this plugin working or what ??

I'm not an expert, but for me with myBB I'd definitely update it to the latest version even if it means that one has to do the above fixes.  They were made to make the Forum safer. 

What you may consider, if you've been having a problem with the plugin, is to remove it first before you do the upgrade, and then to completely download it from an up to date version and reinstall it.  I'd be slightly worried though as looks as though the last build of the plugin is 2014. 
https://community.mybb.com/mods.php?action=view&pid=133

When I checked the last build I also found this cautionary note of the author that may be applicable to your situation:

Please note that this plugin may not be compatible with highly customized themes by default if these themes remove the {$post['groupimage']} or the {$groupimage} variables from the postbit or the profile templates, respectively. If the plugin does not work with your theme, you will need to manually add these variables into your templates.

The above conflict isn't only applicable to this plugin though.  To most plugins.  The more complicated or involved the theme is, the higher the possibility there will be a conflict with a plugin - or if you change the theme, the higher the possibility that it will break the plugin.

In the end though I must give the devil its due. If you spend enough hours on the problem, or discuss it at the mybb.com community forum, you will be able to figure it out eventually. It's never easy though, and it always makes me worry about how secure the script really is in the end. I'd rather go with phpBB since its community forum is much better managed and moderated, and looks as though the Admin there have much higher standards with regard to phpBB styles and extensions. Only drawback with phpBB is that it doesn't have the variety of all of the fancy bells and whistles that myBB has. When I work with phpBB I do miss some of those bells and whistles.