Can I use the set_safe in regular function, which is not view instances ?
// or use the set_safe() method, which is identical to set() but defaults to 'false' $view->set_safe('title', '<strong> bold because unfiltered</strong>');
Yes, you can, by disabling the filter, but is strongly recommended not to, since it disables all security. In general, if you have a lot of need for this, you're doing some wrong.
I told you that twice before. If you want to output HTML, you need to disable encoding.