Answer:
1. You'll create (or copy) CommonEntity.cs manually. You'll create BaseEntity with the OM tool. You'll manually change the inheritance to inherit from CommonEntity.
2. I am not sure about this one.
3. A CommonEntityDataRow.cs is not required. We just used it to show that it could be done.
Here is some additional information for you on the questions that you asked in September. One of the engineers on our team, Jason Kwan, wrote a demo app that shows how to use Abstract class BaseEntity and a separate CommonEntity class that BaseEntity inherits from. So CommonEntity can provide common functions that all inherited objects can use to perform common task. In this case, we simply modified Model’s business object id to a different Common ID. Similar functionality can also be provided through the Abstract Class BaseEntity – BaseID.