Hi Guys,
Anytime a new update is released to C3 and we make that available to the public, it will notify you there is an update available when you launch C3. You aren't forced to update but it is highly recommended since we obviously released the update for a reason. Today's update was critical for supporting updates we made to SONAR. You should install it.
Normally these updates would be released independently of any SONAR update schedule, however they can obviously coincide with one another.
As far as C3's awareness of past product installation, unfortunately this is not supported at this time. C3 will only alert you of whether or not the "packages" (for lack of a better term) it is aware of are up to date or not. By packages, I mean things such as "Engineering FX Suite", which just so happen to contain several plug-ins such as Channel Tools, LP64 Multiband, etc.
As far as restoring hidden products, if you log out of Command Center and then back in, it will restore your cache and show any products you decided to hide.
Lastly, rollback is already available, but only available for products and sub-products that have more then one build available to the public.
I hope that helps answer questions!