Enterprise Manager and Control Center are different products. Your Enterprise Manager will still work even after installing Control Center. 

Yes, we do. You can check out our Wiki pages.

Farm Monitoring and Management lets you view all or any part of your database server farm, giving you the big picture. By analyzing the farm status, health, performance, or resource usage, you can locate the instances that most need attention or work.

You can then drill down into the instances that you want to analyze further or require your attention. This way, you get a natural workflow where you start with the big picture and drill down to the specific instances. By always starting with the farm overview, you ensure that you prioritize the most urgent or needed issues first.

The reporting module includes a report wizard that will let you quickly create the reports you need. Select the instance or group of instances you want to report on, the type and content of the report, and whether to run immediately or schedule for regular runs and automatic distribution to recipients.

No. Changes done via the Control Center application will reflect in your database servers in real-time. But you can schedule jobs to run at a specified time or regular intervals.