After refreshing the page, are the posts merged? If not, then I can only assume that you have incorrectly configured the system of user group rights. You can try to set such settings for checking.
Plugin versions before 3.0.0 support Xenforo 2.2.x. But I recommend upgrading to the latest stable version of Xenforo, because a lot of work has been done in the latest versions of the plugin to optimize the use of server resources.
I tried different options and decided to add an additional field in the "Field" entity and add a filter to the "DefinitionSet" so as not to depend on being on the Index or Category pages.
I don't think I understand you)) Describe in detail what you need. I have Showcase installed and I don't understand what the “self placement” setting is. The showcase uses standard custom fields from Xenforo.