WordPress.org

I've got 404 pages in the admin while browsing ACE submenus

Check the plugin folder location. It should be 'wp-content/plugins/advanced-category-excluder'.

Does this plugin affect my category listing on the sidebar?

Let's say yes, and no.

It can affect if you want to.

Does this plugin support widgets ?

Well, yes and no again :)

We does not support the genuine the calendar, and the recent comments widgets. Thus there is our own recent comments widget. And the calendar is on the way.

Does this plugin works with the newest versions of WordPress ?

We, who update, patch, and develope this plugin alway using the latest stable version, so as far as we are active ( I hope we'll until we reach world domination... :D ) the newest versions will support the most current version of WordPress.

Does this plugin works with older versions of WordPress ?

First of all, I suggest you to take the effort, and upgrade, due to security reasons.

But yes we have the older WP users in our mind, while we develope this plugin.

Does this plugin works for tags?

Not yet ;) But in the future it will :)