How to extend the project area configuration without breaking the inheritance with another project area?

A project area (let's name it B_PA) can inherit a project configuration source from another project area (A_PA) by specifying the second project area in its "Process Sharing" section (the option Use the process Configuration from another project area in this project area).

Then if the process configuration of the project area A_PA is changed (for example to add new work item attribute specific to B_PA) then this change would be also applied in the project area B_PA. However if one changes/overrides elements in the "Project Configuration" tree element of the "Process Configuration" tab of project area B_PA, then the configuration inheritance between both project areas would be broken.

Though it is possible that the inheritance is not broken and the above changes are performed.

My questions are:

1) What would happen if project area B_PA inherits the configuration of A_PA using the "Process Sharing" AND explicitly copy the A_PA configuration configuration source in the configuration source tab of the second project area B_PA? Would the inheritance be broken? What would be the use cases to do so?

2) Is there any document (or any other link) that describes how can the process of project area B_PA be extended without breaking the inheritance with A_PA by changing the source of the process configuration of B_PA?

3) Is it true that changing the presentations of B _PA (for example adding a new attribute) would not break the inheritance?