12i application capability

 1- Is there a capability in R12i that you can modulerise the Oracle applications. For example have GL, AP, PO in one physical server and AR, OM in another server as a part of one Oracle 12i installation and 1 database?        2- Is it possible as a part of 12i application capability to apply Oracle ptach to one Oracle application such as AR12i (Receiavles) and not bring down the other 12i appications down while you are applying the Oracle Patch?

3- Is it true if we have our 12i applications in one server as a primary server and the same instance on another server as a secondary and through Active - Active mode be able to apply oracle patch to Primary server while the entire application is up and running on the secondry server? This means no down time to Oracle12i application. Is this possible? I know some small Oracle patches we may not need any down time but in general any Oracle application family patch, Security patches, Database related patches Can they be done without any downtime?